CERONIA. 81 



much the shorter ; muscular impressions well defined, connected 

 by the simple pallial impression with a small posterior sinus of 

 about the size of" the rounded, muscular impression at its side. 

 Length, one and one half inches ; lieight, one inch ; breadth, eleven 

 twentieths of an inch. I have seen a specimen from Anticosti 

 Island measuring two and one fourth inches in length, and one 

 and five eighths inches in lieight. 



Found abundantly at Plumb Island below Newburyport, and on 

 Nahant Beach ; vast numbers are also thrown up on the outer side 

 of Cape Cod; at Nantucket it is rare. At Sable Island {Willis}, 

 and all along the southeast shore of the St. Lawrence River ; some- 

 times found fossil in its banks at a height of fifteen to fifty feet 

 (Bell). 



There is no longer any question as to the specific value of this 

 shell ; the deauraia of Turton being the same as since described 

 as M. Jauresii. 



Ceronia deaurata. 



Fig. 33. 



Shell ovate, triangular, thick, antiquated, coarsely ridged concentrically, inequi- 

 partite, lateral teeth very strong, curved, faintly striated. 



Maclra deaurata, Turton, Dithyra Brit. 71, pi. .5, fig. 8 (1830). — Flemivg, Brit. An. 



427. 

 Mactra denticulata, Gray in Wood's Ind. Test. Suppl. pi. 1, fig. 9. 

 Mesodemiia denticulata, Gray, Cuv. An. Kingd. (GriiF. ed.) pi. 22, fig. 2. 

 Mesodesma Jauresii, De Joannis, Mag. de Zool. Moll. 183t, pi. 54. — Gould, Invert. 



1st ed. 58. — De Kay, Moll, of New York, 231. — T. Mijller, Synops. Test. 



Viv. 221. 

 Mesodesma diauratum, Hanlet, Kecent Shells, 39, Suppl.pl. 1, fig. 9. — Forbes and 



HwL. Brit. Moll. i. 346. 

 Ceronia Jauresii, CuisNU, Man. de Conch, ii. 79, fig. 342. — Adams, Genera, ii. 414, pi. 



106, figs. 3, 3 a. 

 Paphia deauraia, Gray, Br. Mus. Coll. (Br. Moll.) 157 (1851). 

 Erycina denticulata, Gray, Ann. Philos. 1825 ; Griffith's Cuv. t. 22, fig. 2. 



Shell ovate, triangular, thick and massive, surface rising into 

 ridges at the stages of growth, and covered by a coarse, dusky- 

 brown epidermis ; very inequipartite, behind short and regularly 

 rounded to the base where there is an abrupt turn, and the basal 

 margin continues in nearly a straight line, or is a little arched ; 

 hinge margin also a straight line or slightly concave, anteriorly 

 regularly rounded ; beaks scarcely rising at all, not inclined for- 

 wards ; greatest width of shell midway between the beaks and 



