384 Scientific Proceedings of the 



for the British shell, he has given as synonyms the names of three distinct 

 species. In the " C;italogae of the Animals and Plants of Massachusetts," 

 in Prof Hitchcock's Report of his Survey of Massachusetts, it is set down 

 as Anafina convexa, Wood. In Dr. Storer's excellent translation of Kie- 

 ner's " Iconographie," it is regarded as identical with Th. corbuloides, 

 Deshayes. From this it differs, however, in several important particulars, 

 such as its less elongated form, less truncated extremity, smooth surface, 

 and above all in the palleal impression forming posteriorly a deep and al- 

 most acute angle instead of the semicircular one of Th. corbuloides. The 

 only locality where this shell has been found alive is believed to be Chel- 

 sea Beach. 



Mr. C. conjectured that Mya (Ligula) distorta, Montagu, referred by 

 Kiener to Th. corbuloides, would prove to belong among the perforating 

 CorbulcB ; and to these also he was disposed to refer Anatina truncat^, 

 Turton. Both of them have similar habits of burrowing in the limestone 

 of the British coast. 



July 18, 1838. — G. B. Emerson. Esq., President, in the chair. 



Mr. CouTHOuY, continued his paper on the Osteodesmacca, and made 

 remarks upon the following species. 



Periploma trapezoides, Deshayes. Pariploma insequivalvis, Schum. ; 

 Annfiha trapezoida, Lam. ; Osteodesma trapezoidalis, Blainville. 



Blainville was led into the error of placing this shell in the genus Os- 

 teodesma from supposing it to be identical with Lamarck's Anatina my- 

 alls. But he has committed another serious error in his generic descrip- 

 tion, which has been adopted by Rang in his " Manuel des Mollusques." 

 He says the shell is " inequivalve, la valve gauche plus bombee que la 

 droite," whereas the right valve is more convex than the left. Perhaps 

 they were misled by the peculiar position of the ligament, which is re- 

 markable for being placed anteriorly instead of posteriorly, as in most 

 other shells; a fact not noted in any descripiion. In the very perfect spe- 

 cimen under observation the ossiculum is nearly a complete semicircle. 

 Deshayes speaks of it as triangular. 



Osteodesma hyaltna, Couthouy. Mya hyalina, Conrad. 



The genus Osteodesma, Deshayes, will doubtless prevail over Lyonsia, 

 Turton, and Magdala, Leach, MSS., all of which are founded on Mya 

 Norvegica, Chemnitz, the Amphidesma corbuloides of Lamarck. The 

 name is expressive of the distinguishing feature of the shell. Blainville 

 and Rang were led into the error of supposing Periploma and Osteodesma 

 to be identical ; and Deshayes, though he notices the mistake and refers 

 to his article on Osteodesma in the Encyc. Method, for its actual charac- 

 ters, yet by a singular oversight that article is entirely omitted. Conse- 

 quently, it is to be found only in his recent edition of Lamarck. In the 

 " Catalogue of Animals and Plants of Massachusetts, 1834," it is noted 



