204 DR. p. p. CARPENTER ON NEW MOLLUSCA. 



blunt waves of growth. The shell was sent me as from Dr. Forbes's 

 Vancouver collections, and is so quoted in the Br. Assoc. Rep. 1863, 

 p. 607 ; but Mr. Cuming subsequently stated his belief that it came 

 from Japan. It may be allowable to state that many of the species 

 included in Saxidomus by authors are more correctly rough forms of 

 Tapes, of the d'ecu»sata-tj\)t ; the true Saxidomi differing from that 

 genus (as Callista does from Venus) in having an additional pseudo- 

 lateral anterior tooth. This is very evident in the young shell, which 

 has a much rounder outline than the adult, and can scarcely be 

 distinguished from Callista, except by the absence of lunule. 



252 



