Dr. J . E. Gray on some Families of Bivalve Shells. 23 



I have examined; bxit if there is not some mistake in M. 

 D'Orbigny's description and figure of Cardita spurca, it must be 

 a distinct genus ; however, perhaps he has been misled by the 

 hinder part of the mantle being expanded behind during life, 

 so as to represent a second siphon, which is only a false appear- 

 ance. 



Tellinidce. — The genera Sanguinolaria and Soletellina, which 

 have been referred to Solenidce; Fragilia and Capsa, arranged with 

 Veneridce, should be referred to this family ; they have, like them, 

 two elongated sepai-ate siphons, with large distinct fan-shaped 

 retractile muscles, and the gills not produced into the siphons. 



Anatinidce. — In the May Number of the ' Annals' (p. 413), 

 I referred the genus Mytilimera of Conrad to the family Modio- 

 larcadce with doubt. In an examination which I have been 

 enabled to make of typical specimens of Mytilimera Nuttalli, I 

 think I have discovered the mark left by the shelly plate over the 

 large subinternal cartilage ; and on comparing it with Anatina 

 cuneata, I have as little doubt as one can have from the exami- 

 nation of shells alone (especially in an imperfect condition), that 

 they belong to the same genus and the family Anatinidce. As 

 Mytilimera was published before the Byssonia of Valenciennes, 

 it ought to be retained for these shells. They both have the 

 habit of living imbedded, — Byssonia cuneata in Ascidia, and 

 Mytilimera in sponges. 



Muteladce. — In Mutela the lips are very large, semioval, at- 

 tached by the straight side without the free point existing in 

 Unio and Anodon. 



Cardiadce. — The gills are united together behind the body or 

 base of the foot. 



Solenidce. This family may be thus divided : — 



A. Cardinal teeth 1 • 1. Siphons produced, united ; siphonal muscles 



moderate ; siphonal inflection deep, truncated. 



1. Solen. Shell truncated in front ; umbo anterior ; anterior 

 adductor muscle elongate, horizontal. S. marginatus. 



2. Hypogella. Shell rounded at each end; umbo subanterior; 

 anterior adductor muscle round. II. ambigua, H. vaginata. 



B. Cardinal teeth 2 • 3. Shell rounded at each end. 



a. Siphons moderate, separate ; siphonal muscles small ; siphonal 

 inflection small, truncated. 



3. Ensis. Siphons not produced, separate; umbo anterior; 

 anterior adductor muscle elongate, horizontal. E. Ensis. 



