Deep-water Limpets and Chitons. 21 
tinctly Chiton-like features, and bears additional testimony, 
if such were needed, to the acuteness of Troschel in combining 
(dental characters only being considered) both Chitons and 
Limpets in one dental order. The external form is of course 
partly due to its peculiar habitat; other specimens will no 
doubt eventually be found clinging to some flat surface and 
of normal shape. It seems to be a northern form, and does 
not occur in the Blake collections. 
Suborder PROTEOBRANCHIATA. 
Animal with external branchie. Embryonic shell conical. 
Family Acmeide. 
Gill plumose, cervical. 
Genus SCUTELLINA, Gray. 
Scutellina, Gray, P. Z. 8S. 1847, p. 168,=Scutella, Broderip (not La- 
marck). Type S. crenulata, Broderip. 
The animal of the typical species of Scutellina is unknown ; 
according to Arthur Adams, that of a closely allied species 
(S. ferruginea) resembles Acmea in its externals, except that 
the shell is pure white, with prominently reticulated sculp- 
ture, and the apex is prominent, pointed, and very anteriorly 
situated. Mr. Adams distinctly states that the animal has 
eyes; and it is quite probable that the genus will eventually 
prove to be a good one. 
A specimen was recently obtained, with the dried animal 
(from some West-Indian corals), of a species which is also 
represented in the Blake collection, and which would probably 
be referred, from the shell-characters alone, to Scutedlina, 
though it differs from the received diagnosis of that genus in 
having a blunt subcentral erect apex, much like ordinary 
Acmece, An examination of the soft parts showed, however, 
wide differences from any described genus, necessitating the 
establishment of a new one for its reception :— 
Genus PecTinoponta, Dall. 
Shell resembling Scuwtellina, with a blunt subcentral apex. 
Soft parts resembling Acm@a, except in the following de- 
tails :—Animal blind, with the front part of the head between 
the tentacles and above the muzzle much produced upward 
and forward, extending considerably further forward than the 
end of the muzzle. Muzzle marginated, with lappets at the 
