From Proceedings of the Academy of Natural Sciences of Philadelphia. April, 1862. 



Oa the Classification and Synonymy of the recent species of PHOLADIDJE. 

 BY GEORGE W. TRYON, JR. 



In the year 1851, Dr. John Edward Gray proposed a very excellent arrange- 

 ment of the genera of shells included by earlier conchologists in Pholas and 

 Teredo.* This arrangement has received the approval of most of the subse- 

 quent authors, who have treated on the subject, including Fischer, (Journ. 

 Conchyl., 2d ser., iii. iv.). H. and A. Adams, (Genera of Recent Mollusca,) and 

 Chenu, (Manuel, tome 2.) 



S. P. Woodward, however, in his admirable Treatise on Conchology, part second, 

 makes the following disposition of the Pholades: 



Genus Pholas (including Dactylina, Barnea, Talona, etc. 



" The differences in the dorsal shields are only of specific value." 



Genus Pholadidea, subgenera Martesia, Jouannetia, Parapholas. 



Genus Xylophaga. 



Mr. P. P. Carpenter, in his various works on the West Coast Mollusca, fol- 

 lows Woodward's arrangement. 



The only other modern classification of the family with which I am ac- 

 quainted, is that contained in Swainson's Malacology, which is as follows : 



Order DITHYRA. 



Tribe MACROTKACHLE. 

 Family PHOLIDJE. 



Genera Aspergillum, Clavagella, Fistulana, Gastroch/ena, Pholadomya, 

 Pholas, Phohd^a, Martesia, Xylophaga, Teredo, Teredina. 



I am much inclined to think that more than merely specific value should be 

 attached to the number, form and position of the accessory valves, and I have 

 therefore adhered in the main to Dr. Gray's arrangement. 



The Pholades are monographed by Sowerby, Thes. Conch., ii. 1849. 

 Chenu, 111. Conchyl. ; and Hanley, Desc. Cat., besides which, scattered de- 

 scriptions are contained in the works of numerous ancient and modern authors. 



For very full and satisfactory anatomical descriptions of the animals of 

 Pholadidje, see 



Poli. Testacea utriusque Sicilise. 



Deshayes. Exploration Scientifique de l'Algerie. Mollusques. 



Fischer. Journal de Conch. 2d ser., vols. iii. and iv. 



The Pholades inhabit all parts of the world, and many of the species 

 have a geographical range much surpassing that of the generality of bivalve 

 mollusca; and the supporters of the theory of the specific distinctness of all 



* An Attempt to Arrange the Species of PHOLADIDJE into Natural Groups, by J. E 

 Gray, Ann. and Mag. Nat Hist., 2d ser., viii. p. 380, 1851. 



