30 INVERTEBRATA OF MASSACHUSETTS. 



with two or three cardinal teeth in each valve ; ligament prominent, 

 seated on thick callosities ; palleal impression with a very deep 

 sinus. 



The above generic definition will include all the shells originally 

 embraced in the genus by Blainville, except those of his first di- 

 vision, " shells compressed, thin, with an interior rib passing 

 from the beaks to the basal margin." An acquaintance with the 

 animal has shown the necessity of subdividing his genus. Mr. 

 Sowerby proposes to limit it to the species having the interior 

 bar. But Deshayes, in his edition of Lamarck, has already limit- 

 ed the genus to shells of a different type ; and it would, therefore, 

 seem most proper that any new name which may be given should 

 be applied to other forms. I have, therefore, separated those 

 with the interior bar and other peculiarities for a new genus. 



If we adopt Deshayes' modification of the genus, so that it shall 

 include only ,such as are transversely oblong-oval, covered with 

 obliquely undulating striae, the hinge central, &c., we shall still 

 have another group left, of shells equally distinct in character by 

 their sub-cylindrical, somewhat arched form, compressed at base, 

 the extremities abruptly and usually obliquely rounded, the beaks 

 near the posterior end, the parallel sinus very deep, &c., answer- 

 ing, in fact, to Mr. Conrad's sub-genus CULTELLUS. This would, 

 of course, assume the rank of a genus in case the correctness of 

 the above views should be acknowledged. 



Deshayes says, that the animal of S. Caribous, leg amen, &c., 

 approaches closely to that of the true Solen. But, as the genus 

 Solen now admits only shells with terminal beaks, they must still 

 be arranged under Solecurtus. 



SOLECU'RTUS (Cultellus) CARIBOUS. 



Shell sub-cylindrical^ thick, rounded posteriorly, obliquely trun- 

 cated anteriorly ; beaks nearest the posterior extremity. 



State Coll., No. 224. Soc. Cab., No. 14. 



LISTER ; Conch., t. 421. f. 265. 

 Solen Guineensis, CHEMN. ; Conch., xi. t. 198, f. 1937. DILLWYN; CataL, 62, 



No. 13. BRUG. ; Encyc. Meth., pi. 225. f. 1. 

 Solen Caribse^us, LAM.; Jin. sans Vert., vi. 58. 

 Solecu'rtus Caribous, CONRAD ; Amer. Mar. Conch., 4, f. 3. 



