ANATOMY AND PHYSIOLOGY OF ATRINA RIGIDA. 
437 
5. There is no pallial line but the mantle is attached to the shell at a single point 
just ventral to the adductor muscle. As a consequence the mantle can be withdrawn 
a considerable distance from the edge of the shell. After being contracted the mantle 
again reaches the edge by creeping outward upon the shell. 
6. The spines on the outer surface of the shell are formed by little tongues of the 
mantle which creep out into them during their growth period. 
7. The mantle gland which Menegaux calls the “appendice” is probably a “swab” 
for keeping the mantle free from dirt. 
8. The kidney excretes vacuoles containing quantities of concretions, but little 
protoplasm and no nuclei are thrown off. 
9. Each ganglion supplies a definite region of the body and there is little over- 
lapping. Reflex arcs were shown to exist. 
10. The otocyst is located in the end of the foot far from the pedal ganglion and is a 
variable structure, sometimes consisting of as many as eight lobes and sometimes of 
only one. In one instance three separate ciliated tubes connecting them with the out- 
side were discovered. This indicates that they have arisen from three separate invagi- 
nations of the ectoderm. This is the first instance of this sort found in lamellibranchs 
above the Protobranchia. 
BIBLIOGRAPHY. 
1. Bonnet, R. 
Der Bau und die Circulationsverhaltnisse der Acephalenkieme. Morphologisches Jahrbuch, bd. 3, 
1877, p. 283-322. 
2. Drew, G. A. 
The habits, anatomy, and embryology of the giant scallop (Pecten tenuicostatus, Mighels). Uni- 
versity of Maine Studies, no. 6, September, 1906, 71 p., 17 pi. 
3. Grave, C. 
Investigations for the promotion of the oyster industry of North Carolina. Report U. S. Fish 
Commission 1903, p. 247-341, pi. i-x, 1 map, 1905. 
4. Grave, B. 
Pinna seminuda. John Hopkins University Circular No. 6, June, 1909, p. 46-51. 
5. Grobben, C. 
Zur kenntniss der anatomie und morphologie von Meleagrina sowie der Aviculidae. Im Allege- 
meinen Denkschrift der k. Akademie der Wissenschaft, Mathematisch-Naturwissenschaftliche 
Klasse, bd. 69, 1901, p. 487-496. 
6. Johnstone, J. 
On the structure and life history of the common cockle, with an appendix on the Lancashire 
cockle fisheries. Proceedings and Transactions of the Liverpool Biological Society, vol. 14,1 900, 
p. 178-261, pi. 1— vi and map. 
7. Kellogg, J. L. 
A contribution to our knowledge of the morphology of the lamellibranchiate mollusks. Bulletin 
U. S. Fish Commission, vol. 10, 1890, p. 389-436, pi. lxxix-xciv, text fig. 1-3. 
The ciliary mechanism in the branchial chamber of the Pelecypoda. Science, n. s., vol xi, 1900, 
no. 266, p. 172-173. 
