LAMELLIBRANCHIATA. 579 
Nuculida.]} 
preoccupied names. Salter objected to the adoption of Hall’s name, because it was 
inappropriate and conveyed “an entirely erroneous view of the affinities.” This of 
itself certainly would not be sufficient 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 Tellinomya. He would have placed the species under Nucula or 
possibly Lyrodesma, that being 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 7. 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, 
there 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 hight. 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 
