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



the centre of the ventral range : no siphonal process is to be 

 found, not even an orifice, except the pedal one." — Brit. Moll, 

 ii. 67. Should any of your readers have a specimen of this ani- 

 mal, I should be happy to have the opportunity of examining it ; 

 and also of the animals of any of our species of Lucince. 



I may further remark, that the species of the genus Diplodonta 

 have been confused with the Cyrenella, but the latter may be 

 known by a careful examination of the teeth of the hinge, and 

 the animal differs in having two siphons. 



If M. Mittre's description of the animal of Venus diaphana, on 

 which Recluz has formed his genus Felania, is correct, it will also 

 have to be referred to the Ungulinida. 



While on the subject, I may state, that the genus Myllita of 

 D'Orbigny and Recluz, 'Journ. de Conch.' 1850, 88. t. 11. 

 f. 12-14, is the same as Pythina of Hinds, 1844, Voy. Sulph. 70, 

 and I believe established on the same species. 



Etheriada?. — The lips are very large, seinioval, and attached by 

 the straight side without any free point, as in Mutela. There is in 

 fact no distinct muscular foot in the adult specimens. The body 

 containing the liver projects into the cavity of the mantle, and 

 has been described by Rang as a foot. The foot may be pre- 

 sent in the young state before the shell is attached. 



Through the kindness of M. D'Orbigny, who has sent me the 

 original specimen of his genus Acostea, I am enabled to state 

 that it is identical with the Mulleria of Ferussac and Sowerby, 

 and it appears to be the American form of this family. 



Mytiladce. — The pedal opening of Crenella is small, forming 

 the hinder half or third of the basal margin. 



Malleacea should be divided into three families : — 



1. Pinnadce. Mislead by Rang (Manual Moll. 292), this 

 family was erroneously referred to Mytilacea. Anterior adductor 

 muscle well developed. Gills narrow, very much produced behind, 

 free from each other and the mantle, but fitting against a fold 

 on its inner surface. Rectum with a long tubular process at its 

 base. Vent medial. Pinna. 



2. Pteriadce. Anterior adductor muscle none. Gills narrow, 

 much produced behind, free from each other and the mantle, but 

 fitting against a fold on its inner surface. Rectum simple. 

 a. Avicula, Meleagris, Malleus, and Perna. j3. Crenatula. 



In Avicula the hinder pedal muscle is separate from and in 

 front of the large adductor muscle, with a separate scar ; in Me- 

 leagrina it is close to and forms part of the large scar. There 

 are some other small scars, two in front and one behind the cir- 



