Mollusca in the Collection of the Zoological Society. 369 



because in that species the valves are entirely covered. The branchiae in 

 Ch. vestitus do not reach above half way from the posterior to the ante- 

 rior extremity. 



It may be as well to mention here, that a specimen of Chiton tunicatus 

 of Wood, from the Arctic Ocean, is preserved in the Society's Collection : 

 in that species the branchiae are continued from one extremity to the 

 other. 



Vermetus pellucidus. 



F. testa pellucidd, longitudinaliter striatd, apicem versus carinatd„ 

 Hab. 



The striae, which become carinated towards the apex are best seen in 

 the young shell. This species, in texture, has somewhat the appearance 



of Magilus. 



Patella Mexican a. 



P. testd ovali, radiatim striatd, vertice subcentrali, margine crenulato ; 

 long. 7-^\, lat. o-^\, alt. 2-p»o5 poll. 

 Hah. ad liltora Oceani Pacifici. 



From Mazatlan. This is the largest Patella we have ever seen, some 

 individuals measuring nine inches in length. The young specimens are 

 distinctly, but very closely striated, and their edge is very neatly crenu- 

 lated, but when of large size they are much less neat and regular, and 

 scarcely show any remaining vestiges of the radiating striae. 



-Dentalium semipolitum. 

 D. testd albidd, politd, extremitate posticd subrecurvd, subtilissime 

 striatd, Jissurd posticd nulld ; long. I^Vj l<^^- tV> poll. 

 Hab. 



The very fine striae continue about half the length of the shell, which 

 is rather narrower in proportion than D. nehulosum. 



Bulla calyculata. 



B. testd obovatd, viridi aut castaned, aperturd supernk subcanaliculatd ; 

 labia interna appendiculd calyciformi instructo, intus spirali ; 

 long. /o» lat- To> poll. 

 Hab. ad Insulam Pitcaimi. 



