154 PROCEEDINGS OF THE SCIENTIFIC ASSOCIATION. 
P. seminuda auctt. (as of Lam.) 
P. rigida (Solander) Orb. Wood, Ind. Test. Pinna, 7. 
P. nobilis Chemn. (not Linn.) 
P. orbignyi Hanley, Reeve, C. I. Pinna, 49. 
Mytilus Linne. 
168. M. americanus Favart. 
M. modiolus Chemn. (not Linn.) 
M. tulipa Lam. (part.) 
169. M. brasiliensis Chemn. 
M. guianensis Lam. 
M. semifusca Sow. 
170. M. ligneus Reeve. 
[This species spins a bag entirely covering the shell. 
It is extremely rare, and lives in 2 to 8 fms. water, 
on a bottom of sandy mud. No locality is given 
by Reeve for his shell.] 
171. M. exustus Linn. Orb. Moll. Cuba, pi. xxviii., f. 6, 7. 
M. citrinus Chemn. Wood, Ind. Test. Area, 15. 
M. sulcata Lam. 
172. M. domingensis Lam. Orb. Moll. Cuba, vol. ii., 
pi. xxviii., f. 8, 9. 
M. exustus Lam. 
Crenella Brown 1827. 
173. Cr. viator Orb. Voy. Amer. Mer., pi. lxxxiv., 
f. 84-37. 
Lithodomus Cuvier 1817. 
174. Li. bipenniferus n. sp. 
Elongate, sub -cylindrical, nearly straight, smooth, 
thin, epidermis yellowish-brown, generally incrusted 
with a blackish deposit, running posteriorly into white 
