22 Dr. J. E. Gray on some Families of Bivalve Shells. 



rect, and that it has only a single opening like Crassatella and 

 Cardita. The family must, therefore, be removed to the order 

 Unio?iacea, between Carditidce and Crassatelladce, differing chiefly 

 from the latter in the external position of the cartilage. 



Most probably, when the animal of Astarte is alive, the hinder 

 portion of the mantle near the anal aperture forms a siphon-like 

 aperture, as is the case in Crenella and in many of the other 

 Lucinacea. It has been suggested that perhaps the leaves of the 

 mantle are united together and form a siphonal aperture when 

 the animal is alive, but separate when the specimen has been kept 

 in spirits ; however, there is not the slightest appearance of any 

 such union on the surface of the mantle, and it certainly is not 

 the case with Crenella, Mytilus, Unio, Anodon, and other animals 

 which are without a branchial siphon, and which have an imper- 

 fect siphonal aperture for the entrance of the water to the gills. 



Carditid/E. This family may be thus divided : — 



A. The elongate hinder cardinal tooth in left valve single, trigonal, 



upper lamina of it rudimentary or quite wanting. Shell strongly 

 costate, cordate or ovate. 



1. Venericardia. Shell short, cordate, hinder cardinal tooth 

 triangular. V. australis, V. ajar. 



2. Cardita. Shell elongate, ovate, hinder cardinal tooth elon- 

 gate. C. antiquata. 



B. The elongate hinder cardinal tooth in left valve double, both 



lamina equally developed, elongate. Shell elongate, oblong. 



3. Mytilicardia. Shell oblong, strongly costate ; front hinge- 

 tooth triangular, diverging; anterior lateral none. M. Jeson, 

 M. concamerata. 



4. Lazaria. Shell oblong, strongly costate, front hinge-tooth 

 compressed, anterior lateral tooth distinct. L. Pectineus, L. ra- 

 diata. 



5. Azarella. Shell roundish, compressed, dilated behind, 

 striated; front hinge-tooth elongate, compressed, similar and 

 parallel to hinder; lateral teeth none. A. semiorbiculata, A. gu- 

 bernaculum. 



In Astartida I inserted " Cypricardia sp. according to D'Or- 

 bigny ;" this was a mistake for Cardita sp. M. D'Orbigny both 

 describes and figures Cardita spurca, t. 82. f. 13, as having two 

 distinct siphonal apertures. I have not been able to see the 

 animal of this shell. M. Quoy describes the animal of Veneri- 

 cardia australis. Deshayes figured the animal of Cardita caly- 

 culata as having only a single anal siphonal opening, and this 

 is the case with the animal of the several species of Cardita 



