gie' for 1844, page 12, that Menestho stands between Scalaria and Velutina. His allocation of other genera constituted by Möller are less happy: e. g. Amaura, between Natica and Margarita; and Admete, between Mitra and Lottia. It is certainly not the Monoptygma of Lea, which has an obliquely spiral fold on the pillar. Couthouy placed a North-American species (striatula), allied to the present, in Brown's genus Pyramis, the type of which is Eulima subulata. Pyramis striatula of Couthouy has been referred by Stimpson and Binney to the Menestho albula of Möller; but it is very much larger and more cylindrical, and the sculpture is different.

O. albula appears to be the sole representative in the Arctic seas of the numerous family of Pyramidellidæ.

XX.-Description of Niphargus puteanus, var. Forelii.
By ALOIS HUMBERT*.

THE existence of Amphipod Crustaceans living in wells and more or less deprived of visual organs was indicated in 1835 at Paris and in Germany. MM. P. Gervais and C. L. Koch, who were the first to discover them, referred them to the genus Gammarus. Some years later, Schiödte, who had discovered a species of the same group in the caverns of Carniola and Istria, perceived that these subterranean crustaceans deserve to form a distinct genus, to which he gave the name of Niphargus, which is now generally adopted.

A great number of memoirs have since been published upon these animals; and these have furnished us with much information as to their organization and geographical distribution. New species of the genus Niphargus and even new genera allied to the latter have been discovered, both in the subterranean waters of wells and caverns and in the sea. Finally, in 1869 M. F. A. Forel indicated for the first time the existence of blind Gammaridæ (Niphargus) in the depths of the lake of Geneva, and in 1873 he found the same animals in the lake of Neuchâtel.

Although we may say that our knowledge of the Crustacea of this group has been greatly extended, we must unfortunately add that the subject still presents many doubtful points, and

* Translated by W. S. Dallas, F.L.S., from an abstract by the author in the Bibliothèque Universelle: Archives des Sciences,' 15th January, 1877, pp. 58-75. The original paper appeared in the 'Bulletin de la Société Vaudoise des Sciences Naturelles, tome xiv. (1876), pp. 278-398, pls. 6 & 7.

that the most divergent opinions are still entertained as to the value of the different specific and generic forms.

The Niphargi observed by Caspary, Hosius, and De la Valette-St.-George were described under the name of Gammarus puteanus, invented by C. L. Koch. Schiödte distinguished two other species in his genus Niphargus, which also includes this Gammarus puteanus. One of these, obtained from the Austrian caverns, is his N. stygius; the second, found in a well in England, is his N. aquilex. Spence Bate has introduced two new species under the names of N. fontanus and N. Kochianus. Costa has described a Gammarus longicaudatus. Joseph has indicated a new species from the caverns of Carniola under the name of G. orcinus. Czerniavski has described a Niphargus ponticus from the Black Sea. Lastly, we must also refer to an old species described by Leach under the name of Gammarus subterraneus. The genus Eriopis, established for a marine species (E. elongatus) found off the shores of Scandinavia at a depth of from 40 to 60 fathoms, seems to be synonymous with Niphargus. Finally we have to mention a very nearly allied but easily distinguishable generic group, the genus Crangonyx, Sp. Bate, the only known species of which (C. subterraneus) has been found in a well in England.

According to M. de Rougemont*, to whom we are indebted for the latest work published on this subject, a great part of these specific and generic names ought to disappear, as they apply only to different forms simply representing the successive stages of development of a single species. Among the specimens collected by him in a well at Munich, M. de Rougemont has found five distinct forms, which, however, are transformed one into the other. The first, which is from 2 to 4 millims. in length, corresponds with Crangonyx subterraneus, Sp. Bate, and Gammarus pulex minutus of Gervais. The second, varying between 3 and 6 millims., is the N. Kochianus, Sp. Bate. The third, measuring from 5 to 8 millims., is referred to the Gammarus puteanus of Caspary and Hosius. The fourth (12-14 millims.) is assimilated to the N. fontanus, Sp. Bate †. The fifth (12-18 millims.) is determined as the

*Philippe de Rougemont, 'Naturgeschichte von Gammarus puteanus, Koch,' Inauguraldiss., 8vo, pp. 40, Munich, 1875. More recently M. de Rougemont has published in French, under the title of 'Etude sur la Faune des eaux privées de lumière' (4to, with 5 plates, Paris, 1876), a memoir, which contains a translation of that above cited, together with a description of Asellus Sieboldii and observations on a Hydrobia found in a well at Munich.

We reproduce this synonymy with great reserve, because there are contradictions between M. de Rougemont's text (p. 23) and his table of species (p. 29) with regard to the third and fourth forms.

N. stygius of Schiödte and the N. puteanus of Koch. To these five forms observed at Munich, M. de Rougemont adds a sixth found in a well at Neuchâtel, and measuring 33 millims. in length. Besides its colossal dimensions, the specimen from Neuchâtel is distinguished by a considerable number of joints (51) in the superior antennæ, and by the almost complete disappearance of the accessory flagellum, which only shows itself in the form of a mere spine.

It is to be regretted that the author, who has himself dredged Niphargi in the lake of Neuchâtel, does not tell us whether these Crustaceans fall under any one of the six forms which he establishes for the Gammaride of the wells.

M. de Rougemont was struck with the discovery in a single well of five different forms, and found it difficult to believe that five species so nearly allied to each other should live together in so limited a space. He sought in vain for small specimens representing the young condition of the larger forms. Out of about a hundred individuals he found none of the dimensions of 2-4 millims. which approximated to the form which attains 18 millims. He then asked himself, whence came these large individuals? and he arrived at the conclusion that these five forms are not species, but only different stages of development of one and the same species, namely Gammarus Duteanus, Koch.

Thus, according to him, something of the same kind would take place here as in the case of the salmons, which, when they are not more than 6 inches long, already present completely developed reproductive organs and nevertheless continue to grow until they attain a length of 5 feet. In the Gammari, as in the salmons, characteristic forms would seem to make their appearance as the animal increases in age. This naturalist isolated certain forms, with the object of ascertaining whether they really underwent metamorphoses. His experiment was successful. He saw individuals pass by change of skin from the first form (Crangonyx subterraneus) to the second (Niphargus Kochianus); and he also observed the transformation of the fourth form into the fifth. Hence the author concludes that the genera Crangonyx and Niphargus must not be separated, since they only represent different states of one and the same species. He goes even further, and proposes the suppression of the genus Niphargus, which he regards as being nothing more than the result of a modification of Gammarus pulex.

The facts upon which M. de Rougemont relies are doubtless very curious and of much significance. It cannot be denied that we have in them observations worthy of the utmost attention on the part of zoologists. I think, however, that we

cannot without reserve accept all the combinations of species and genera proposed by this author. Side by side with very interesting observations expounded most ingeniously, M. de Rougemont's memoir contains a certain number of weak points, which prevent our being completely convinced by it. In the first place the discordancy between different parts of the text with respect to the arrangement of the old species under the different forms observed leaves room for doubt as to the validity of the proposed identifications. Other things also increase our distrust in this respect. Thus fig. 4 on pl. i. represents the last two joints of a foot, reputed to be those of the two anterior pairs of the fourth, fifth, and sixth forms. Now if we compare this figure with that given by Bate and Westwood of Niphargus fontanus, it will be seen to differ completely. The species of the English authors would be still more difficult to recognize in fig. 3, which represents the second and third forms.

The figures of the two anterior pairs of feet of the first form are different from those given by Bate and Westwood for Crangonyx subterraneus; and it is the more difficult to decide whether M. de Rougemont really had this genus under his hands, because he does not tell us whether his specimens presented the entire telson and the last pair of feet with a single unjointed ramus, which are important characters serving to distinguish Crangonyx.

Lastly, my observations on the Niphargi of the Lake of Geneva do not agree with those of M. de Rougemont. Among the animals of this genus communicated to me by M. Forel, some are very small, measuring 2 millims. from the front of the head to the extremity of the last saltatory feet. These individuals ought therefore to take their place under the first form of M. de Rougemont, including all the specimens from 2-4 millims., and consequently correspond to Crangonyx subterraneus, Bate. But this is by no means the case. These young individuals undoubtedly present certain differences dependent on age, and consisting in a much smaller number of joints in the antennæ, a smaller quantity of setæ upon the different parts of the body, &c. But as to the generic characters properly so called, they are already well marked; and in particular the first two pairs of feet have already the same form as in the adult, and the telson is deeply cleft.

It seems to me, therefore, that whilst we must take account of M. de Rougemont's observations as furnishing a very valuable indication of the metamorphoses which the crustaceans of the group under consideration may undergo, we cannot yet definitely accept the changes which he proposes in the classification of the forms hitherto observed. I have there

fore provisionally retained the genus Niphargus, modifying it and completing its diagnosis.

In the state of confusion which prevails at present among the species of this genus their determination is difficult, whether we accept the arrangement of Schiödte and Spence Bate, or, like De Rougemont, only regard the forms described as representing the successive phases of a single type.

The Niphargus of the Lake of Geneva, and that which I have found in a well in the environs of Geneva, although very different in size and presenting some slight differences of organization, did not seem to me to need separation otherwise than as varieties. This point once settled, I had to inquire whether the species was new, or whether it fell under one of those which were already described. It seemed to me to be quite distinct from N. aquilex, fontanus, and stygius, and, although more nearly allied to N. Kochianus, could not be confounded with it.

As to the six forms of M. de Rougemont, there is not one. to which I could with any probability or confidence refer those which I have before me. The figure given by that author representing the last two joints of a foot of the fourth, fifth, and sixth forms, resembles these same parts in my specimens; but as I have already stated, that figure is not in accordance with some of those of the authors quoted.

It will be always difficult to arrive at a decided opinion with regard to the Gammarus puteanus of Koch, which is described and figured in a very unsatisfactory manner. Nevertheless the name given by Koch has been in a manner fixed in science by the memoirs of Caspary and Hosius, who have given very good figures of the species. Thus it seems to me that, until the contrary is proved, we may regard the name of Gammarus puteanus as applying to the species which has been described and figured by these two authors. Now it is to this that my two varieties seem to approximate most closely, notwithstanding slight differences in the proportion of the propoda of the first two pairs of feet. I have consequently adopted for the species the name of Niphargus puteanus, Koch, distinguishing each of the two local varieties, however, by a special name: the form from the Lake of Geneva is Niphargus puteanus, var. Forelii; and that found in a well at Onex, N. puteanus, var. onesiensis. I have completely described only the former, and contented myself with indicating the differences which exist between it and the second form by placing in a tabular form those which seemed to me well marked. A detailed comparison with the type of the preceding authors is impossible, because the latter has not been described with sufficient exactitude.