tinctly skirted with a fringe or superficial wash of ash, buff or olive, which more or less quickly disappears, often by the double process of abrasion and fading. Exposure to the elements and friction also produce more or less marked change in color where there is no conspicuous loss of tissue from the border of the feather. Generally this is simply an obvious loss of color by fading, but in some instances the color becomes somewhat heightened, as in the case of some browns which change from a grayish brown to a more reddish tint; this may be due in part to abrasion, but probably somewhat also to chemical action consequent on exposure. In such changes, however, there is no transposition of pigment, nor any radical modification of pattern-no "redecoration," and no transformation of white feathers into black-but merely a slight change in tone.

It is noteworthy that while many writers have believed in and have advocated change of color in feathers, of even the most radical kind, the theories as to the causes and methods of the change are as diverse and as numerous as their ingenious inventors. In several instances the fat of the body has been presumed to be the vehicle of the colored secretion that is supposed to flow, by imbibition, or capillarity, or by some unknown process, from the body into the feather; in one case (Fatio) it is not a vehicle for the transportation of pigment, but merely a solvent for the pigment granules already in the feather; in another case a 'secretion' (not a fat) flows from the body into the feather and spreads by endosmose to its remotest cells, depositing in layers the pigment it carries till the feather is duly colored (Severtzof). How the supposed secretion, which mechanically (not physiologically) acts as the coloring agent becomes charged with its burden of pigment no one really attempts to explain; yet some of these theory builders do confess themselves puzzled to understand how under this mechanical or 'purely physical' (Severtzof) process the pigments can so accurately assort and arrange themselves as to produce the color patterns of variegated feathers.

While there may be a slight basis in fact for some of these speculations, if there really is such a thing as an increase in the quantity, and any radical change in the position, of the pigment in a dead feather, it is still, as stated by Bachman in 1839, by

virtue of some new law of nature not hitherto discovered." Finally, as has already been stated in substance, the inventors of these diverse theories have assumed, and attempted to explain, conditions that in nine cases out of ten had no existence; namely, a color change, demonstrably due-normally at least-to molt, which they have supposed must happen in some other way.

Supplemental Note on the Spring Molt of the Bobolink. Since the foregoing was made up for the press I have had opportunity, through the kindness of Mr. Thomas Proctor of Brooklyn, of examining twenty-five live Bobolinks (Dolichonyx oryzivorus) in the bird stores of that city, and two others in Mr. Proctor's own extensive aviary. The examination was made on the 14th of March, and the molt was in all stages, from birds showing only here and there the tip of a black feather on the breast, to those that were in nearly full breeding dress. A large number were in the highest stage of the molt, pin-feathers being distinctly visible, especially among the wing-coverts and scapulars and interscapulars, even when the birds were several feet distant. Generally the black appeared in patches scattered irregularly through the autumn plumage; on the lower parts, where the change was most striking, sometimes the black prevailed and sometimes the olive buff tints of the fall dress. In short, the birds presented the same conspicuously pied appearance seen during the molt at the end of the breeding season, except that the incoming colors were reversed, the black now replacing the autumn dress instead of the

reverse.

Of course, since the publication of Mr. Chapman's papers 'On the Changes of Plumage in the Bobolink' (cited antea, p. 42, footnote 2), there has been little reason to doubt that the Bobolink acquired its breeding dress by a spring molt; yet as his conclusions were based on the examination of scanty material, and as there has been a tendency in some quarters to question their correctness, and as the contrary has often been asserted (see the case of Ord, antea, p. 16), it seems worth while to record in this connection the overwhelming proof of the fact I am now fortunately able to adduce.

Article IV.-NOTE ON MACROGEOMYS CHERRIEI

(ALLEN).

By J. A. ALLEN.

PLATE I.

In December, 1893 (this Bulletin, V, p. 337) I described as new a form of Geomys from Costa Rica, under the name Geomys cherriei, the description being based on a single immature specimen. The species was redescribed from the same specimen and the skull figured by Dr. C. Hart Merriam in his' Monographic Revision of the Pocket Gophers' (North Am. Fauna, No. 8, p. 194. Pl. xv, Fig. 1, Jan., 1895), under the name Macrogeomys cherriei (Allen). Through the kindness of Señor Anastasio Alfaro, Director of the Costa Rica National Museum, I have before me five additional specimens, four of which are fully adult, and the other about half grown. The six specimens differ very little in coloration, all being dark sooty or plumbeous brown above and light, soiled grayish white below, slightly darker or more ashy gray over the pectoral region, the line of demarkation between the upper and lower surfaces being well defined. They all possess the prominent squarish or subtriangular white patch on the top of the head noted in the type, and thought possibly due to albinism. It proves, however, to be a normal and striking feature of the coloration. As regards external characters, there is nothing further to add to the original description, the skins being unfortunately not in condition to admit of satisfactory measurement. Señor Alfaro (in litt. May 31, 1895) says, however, that an adult male measures: head and body, 230 mm.; tail, 90 ; total length, 320. In the adults the length of the hind foot averages about 45 mm.

An adult male skull measures as follows: Total length (condyle to front base of incisors), 59 mm.; zygomatic breadth, 39; greatest breadth across squamosals, 33.5; interorbital breadth, 10; breadth of muzzle at root of zygoma, 13.5; length of mandible (without incisors), 14; greatest breadth of mandible at the

angular processes, 37.5; length of upper molar series (crown surface), 11. Ratio of zygomatic breadth to total length, 66. From Señor Alfaro I learn that all of these specimens, including the type of the species, were taken on his father's plantation Santa Clara,' in the small town of Jiménez, on the Atlantic slope, at an altitude of only 700 feet above the sea. He also writes that Geomys heterodus Peters, which he describes as a very different animal from M. cherriei, is found only at an elevation of 6000 to 7000 feet. M. cherriei is very abundant about Jiménez, and very destructive to the coffee plantations. Seventy were taken in a single month on his father's estate.

The Museum is indebted to Señor Alfaro for several specimens of this interesting species, the type of which (Am. Mus. No. 10768) is also now the property of the Museum.

The accompanying figures (Pl. I) represent the skull of an adult male (Am. Mus. No. 1), natural size. The specimen was taken at Jiménez, Costa Rica, in May, 1895, and forms one of the series referred to above.

Article V.-ON MAMMALS COLLECTED IN BEXAR

COUNTY AND VICINITY, TEXAS, BY MR. H. P. ATTWATER, WITH FIELD NOTES BY THE COLLECTOR.

By J. A. ALLEN.

The Museum has recently received from Mr. H. P. Attwater, of San Antonio, Texas, about 400 specimens of mammals, collected chiefly in the vicinity of San Antonio, in Bexar County, but including many from Kerr County. The specimens represent 37 species, on which Mr. Attwater contributes valuable field notes, and also important information on 10 other species found now or formerly in the vicinity of San Antonio. These are mainly the larger Carnivores and the larger game animals, as the Deer, Bison, etc., which are all now rapidly disappearing from the State. It hence becomes desirable to place on record the notes on their former status contributed by Mr. Attwater.

I am also indebted to Mr. Attwater for the following sketch of the topographic and other features of the region, and for interesting notes on the effect upon animal and plant life of the severe and long-continued droughts that periodically visit this portion of Texas.

CHARACTER OF THE REGION.Bexar County is on the line of junction of two regions of diverse topographic character, and is thus faunally a point of special interest, forming, as it does, about the eastern limit of various western forms, and the western limit of various eastern forms of animal and plant life. At about this point also various northern forms find their southern, and various southern forms their northern limit of distribution.' The following somewhat detailed account of the region is from Mr. Attwater's MS. notes.

"The city of San Antonio has an altitude of 680 feet above sea level, and is situated about 150 miles northwest of Rockport and

1 Cf. Attwater, The Auk, Vol. IX, 1892, pp. 229, 230.