26 SPECIES OF THE SYSTEMA. 
good, the shell has usually been regarded as a variety of stri- 
atus. The expression “ arcuato-striate,’ however, reminds one 
of the following remark, in Sowerby’s ‘ Thesaurus,’ upon the 
little P. cuneiformis of Say: ‘“ Resembling striata, but with 
the striz or ribs of the anterior part curved, not angular.” The 
P. pusillus might perhaps be referred, with a note of interroga- 
tion, to that American species. 
Pholas crispatus. 
The Pholas crispatus of authors (Wood, Gen. Conch. pl. 15, 
f. 3, 4, 5) still remains, in our author's cabinet, in its marked 
receptacle, and alone of the Pholades present displays the re- 
quired characteristics. The details of the ‘Museum Ulrice’ 
and the cited figure in Lister (Angl. pl. 5, f. 38) rendered the 
determination of the species an easy task: the additional refer- 
ences in the manuscript to “ Pet. Gaz. t. 79, f. 18,” and “ List. 
t. 436,” confirm the identification. The following note is from 
the pen of Linnseus : — “ Habet dentem vacuum porrectum ut 
Mya, sed margo posticus recurvatus ut Pholas. Strie testarum 
hine scabre, inde leves. Differt a reliquis dente intus recurvato 
vacuo. Testa multum hians connectit cum sequente.” - 
MYA. 
To his generic definition our author had intended to add 
“margo longitudinaliter elevatus,’ in contradistinction to the 
“margo recurvatus” of the preceding genus, and had formed 
anew genus, UnEepo, for the fresh-water species pictorum and 
margaritiferus. 
