Nucuiiteo LAMELLIBRANCHIATA. 579 



preoccupied names. Salter objected to the adoption of Hall's name, because it was 

 inappropriate and conveyed "an entirely erroneous view of the aflBnities." This of 

 itself certainly would not be suflBcient to invalidate the name, yet some weight 

 attaches to it when considered in connection with other defects. Salter justly 

 observes that "the chief characters of the genus reside in the hinge and teeth, 

 which are neither figured nor described by him (Hall), casts only of the interior and 

 external surface having been given in the plates of his excellent work, nor was the 

 external ligament observed." This is all strictly true and, what is more, it is scarcely 

 to be doubted that if Hall had observed the nuculoid character of the hinge he would 

 not have proposed TeUinomyq. He would have placed the species under iVwcM/c or 

 possibly Lyrodesma, that be,ing the arrangement adopted by him in all cases where 

 he did see the ctenodontoid hinge. Nor can we doubt that Ctenodonta was acceptably 

 described at least five years before Tellinomya, Hall, was redefined in accordance 

 with the true character of the shells upon which the genus was founded originally. 

 Finally, the original description of Tellinomya was so totally at variance with the 

 facts that Salter could not for a moment be blamed for failing to recognize the 

 identity of'T. nasuta and the shell which he proposed to call Ctenodonta. 



Taking all these defects-of Tellinomya into consideration, I do not see how we 

 can do otherwise than adopt Ctenodonta in preference to Hall's name. Had Tellin- 

 omya not been preoccupied I would have suggested another solution of the difficulty, 

 .namely, to subdivide the genus so that both names might be used, at least provision- 

 ally, Tellinomya for the typical group of species and Ctenodonta for the. higher and 

 round or subtriangular forms like C. astartiformis Salter. But being preoccupied, 

 thfere is no room for Tellinomya in this connection. 



Taken as a whole, the genus Ctenodonta is a remarkably complex group of 

 species. This may perhaps be accounted for by the great number of the recog- 

 nizable forms, yet it is more likely the result of too great an expansion of the 

 generic limits. Indeed, the variety of characters exhibited in the genus as now 

 accepted is so great that it is difficult to draw up a satisfactory description without 

 becoming unusually circumstantial. Thus, there are elongate shells and others in 

 which the length is exceeded by the bight. In many the outline is elliptical, in some 

 subrhomboidal, in others rounded and in a few subtriangular. In some the umbones 

 are compratively large and full, in others very small, and the beaks may be turned 

 either forward or backward. Internally the structure is equally diverse. The hinge 

 plate may be narrow or broad, nearly straight or bent rectangularly, and with out- 

 wardly or inwardly bent denticles. The latter, though always smallest near the 

 beaks, may form a continuous series from one end of the hinge to the other, or the 

 continuity of the series may be interrupted beneath the beak. This interruption 



