countless blue-bottles; the humming of bees, the shrill buzzing of wasps, and the creaking sound of the sawyers, are, I presume too well known to need description. The last of these is the Tenthredo cerasi so destructive to many of the fruit trees of North America, and the sound produced by its sawing efforts is entirely mechanical. So also is that of the timber-louse, Atropos pulsatorius, which in this respect resembles the death-watch, but belongs to the Neuroptera, and reminds me that the same family includes the celebrated Termes or White ants. Ants belonging to the Hymenoptera are well known as domestic pests, from their ravages some times in the well-stored cupboard; and when a swarm of them is dispersed, the only sound emitted for so unceremoniously driving them away, is a distinct and audible kind of a hiss.

I trust this slight sketch of the generation of sounds of insects, heard for the most part on the Island of Montreal, may prove not only of interest, but be the means of drawing attention to the subject. Many of them are not only exceedingly shrill, but can be heard at a considerable distance, and with every propriety the organs producing them in nearly all the insects which have been noticed, may be considered as the analogues of the larynx and trache in the higher animals. I am of course at issue with the immortal Cuvier on this point, as he has remarked that the various noises made by insects are in reality not the voice; because, he says, the air does not pass through a larynx. If the numerous spiracles are for the purposes of respiration, a fact indisputably established, and that the air is known to rush in and out of some of them, then they are the analogues of the larynx, and simulate its functions, as much so, as the circulation in insects is the counter-part of the same function in the vertebrata. And I will close with the question of Pliny on this subject, who asks-" And where too, has nature implanted that sharp, shrill voice of the creature, so utterly disproportioned to the size of its body?" to which I reply, that in the majority of insects, it is in the spiracles, or representatives of the larynx in higher animal life.

London, September, 1858.

ARTICLE IX.-On some new Genera and Species of Brachi-
opoda, from the Silurian and Devonian Rocks of Canada.
By E. BILLINGS, F.G.S. Read before the Natural History
Society of Montreal, 28th March, 1859.

(From the Report of the Geological Survey for 1858.)
Genus CENTRONELLA, Billings.

Generic Characters.-Shells, having the general form of Terebratula. Dorsal valve, with a loop consisting of two delicate riband-like lamellae, which extend about one-half the length. These lamellae at first curve gently outwards, and then approach each other gradually, until at their lower extremities they meet at an acute angle; then becoming united they are reflected backwards towards the beak in what appears to be a thin flat vertical plate. Near their origin each bears upon the ventral side a single triangular crural process. Name from the Greek, Kentron, a spur. This genus is intermediate between Terebratula and Waldheimia. In the former the loop is short, not exceeding greatly one-third the length of the shell and not reflected. In the latter it extends nearly to the front and is reflected but the laminae are not united until after they are folded back.

The following figures will explain the difference more clearly:

Figs. 1, 2, 3. Ventral, side, and dorsal views of Centronella glans

fagea.

แ

4. Interior of dorsal valve, shewing the loop.

5. Longitudinal section, shewing the position of the loop

in the interior.

Interior of dorsal valve of Terebratula. 1, the loop.

7. Interior of Waldheimia. 1, the loop.

CENTRONELLA GLANS-FAGEA, (Hall, Species.)

Rhynchonella glans-fagea, Hall. Report of the Regents of the University of the State of New York, 1857. Page 125. Description.-Shell, small, smooth, broad oval or rather subrhomboidal, greatest width near the centre of the length of the dorsal valve, from which point the sides slope in nearly straight lines to the beak where they meet at an angle of about eightyfive degrees; front rounded or sometimes either a little pointed or slightly sinuated. Ventral valve the larger, its outline forming a nearly regular arch from the beak to the front margin, strongly and broadly subcarinate along the centre, beak very prominent and projecting over the dorsal valve at a right angle but not much incurved at the point; an open foramen beneath it. Dorsal valve somewhat flat, a wide shallow concavity extending from near the beak to the front where it gently elevates the margin of the ventral valve. Length from two to four lines, width about the same.

This little species is somewhat variable in form, the length being sometimes greater than the width, and often a little less. The broad shallow mesial depression of the dorsal valve sometimes extends nearly to the beak, and in other specimens dies out at two thirds the length. The detached dorsal valves also exhibit two very thick and strong supports for the loop and between them a deep fissure open to the beak.

Locality and formation.-Oriskany Sandstone, near Cayuga, C. W. Corniferous limestone at Rama's farm, near Port Colborne; abundant. In the State of New York it occurs in the Schoharie Grit.

Genus STRICKLANDIA, Billings.

Generic Characters.-Shell, usually large, elongate oval, transversely-oval, or circular, sometimes compressed; valves nearly equal; a short mesial septum in the interior of the ventral valve supporting a small triangular chamber beneath the beak as in Pentamerus; in the dorsal valve no longitudinal septa spires or loop, the whole of the internal solid organs consisting of two very short or rudimentary dental plates, which in some species. bear prolonged calcified processes for the support of the cirrated arms. In all the species the ventral valve has an area more or less developed.

This group of shells, although closely related to Penta

merus, differs from that genus in the following particulars :— 1st. In Pentamerus the form is globular and the ventral valve is much the largest. In Stricklandia the valves are nearly equal and never globose. 2nd. In Pentamerus the dorsal valve has two or three longitudinal septa, which in some species sustain a small triangular chamber. In Stricklandia these characters are entirely absent. It might be thought that the difference between the short or rudimentary dental plates of Stricklandia and the elongated mesial septa of the dorsal valve of Pentamerus is not of sufficient importance to constitute a generic distinction, because it is only a difference in the extent to which identical parts are developed, the dental plates of the former genus being a rudimentary state of the septa of the latter. When, however, we examine any group of closely allied genera we find that all the grounds for separation consist in the various modifications of the same set of organs. Were it not so then there would be no such thing as homologous parts. The difference in the degree of the developement of an organ is not always a good character, but when it is carried to such an extent that the whole form of the animal is affected in a particular manner, manifested in a number of species then it becomes of generic value. If we take the several species of Stricklandia and compare them with an equal number of species of Pentamerus, such for instance as P. Knightii, P. galeatus, P. Sieberi, P. acutolobates, P. caduceus, &c., the difference in the external form of the two groups is so remarkable that we would be almost warranted in separating them into two genera upon this ground alone; but when to the dissimilarity in the general form we add the difference in the internal structure then there can be little doubt as to the correctness of the separation.

This genus includes three English species which have been long known under the names of Pentamerus lens, P. liratus, and P. lavis. All these, and the three Canadian species, abound in rocks of the age of the Middle Silurian, such as the Landovery rocks of Sir R. Murchison, and the Clinton and Niagara groups of the New York geologists. No species have as yet been found either above or below the Middle Silurian. On the other hand, the genus Pentamerus occurs more or less frequently in all formations from the Black River limestone* to the Devonian inclusive.

I have ascertained that Atrypa hemiplicata (Hall) is a true Penta

merus.

The following figures exhibit the difference in form between Stricklandia and Pentamerus :

do. do., side view.

"L 9.
"10. Pentamerus Knightii, side view.

I am not certain whether Fig. 9 is the true S. lens or a variety. It is more pointed in front than any of the English specimens that I have seen.

STRICKLANDIA, GASPÉENSIS, Billings.

Description.-Shell, large, oval; length to breadth about as five is to four; valves about equally convex. The ventral valve has a shallow mesial depression which commencing at the beak in a point gradually enlarges to the front margin, more than half of which is affected by it; the dorsal valve has a corresponding mesial elevation, on each side of which there is sinus of just sufficient strength to induce the idea of a trilobed surface. The two valves are nearly equal, the ventral being the longest by about one line in a specimen five inches in length. The beak of the ventral valve is closely incurved over that of the dorsal and on each side of it there is a short area. The whole surface is covered with strong close rounded longitudinal ribs with rather sharp furrows between. These ribs are on an average one line wide at the front margin.

This species, differs from all the others in its form, which is a nearly perfect ellipse, both ends being about equally rounded and the greatest width being in the centre of the length. The ribs are also more distinctly defined and proportionally more numerous than these of any other species.

The average length is four inches; width three inches and a half; depth of both valves two inches and a half.