12 Mr. W. H. Dall on certain 
the connexion of certain peculiarities of structure in them 
with their geographical distribution, and the progressive de- 
velopment indicated by the characters of different genera, 
have already been the subject of comment by me*. 
The forms of lowest organization and least specialized 
characters among those already known are those which inhabit 
the deeper water; hence there was reason to suppose that 
features of much interest would be exhibited by the few speci- 
mens which had just been brought up from much greater 
depths than any from which limpets had hitherto been 
obtained. 
The examination was rendered more complete by the pos- 
session of additional specimens, which are contained in the 
deep-sea collection from the Antilles, made by Prof. Alex. 
Agassiz and Lieut.-Commander Bartlett, U.S.N., on the 
United-States Coast-Survey steamer ‘ Blake.’ These afforded 
valuable confirmation of impressions derived from the study 
of the material obtained from Prof. Verrill. 
Some of the specimens obtained are of unusual interest, as 
showing a combination of characters which has heretofore 
been unknown in animals of the same order. While the 
shells present few salient features, the soft parts show extra- 
ordinary and unexpected characters. They are divided into 
representatives of the orders Riphidoglossa, Docoglossa, and 
Polyplacophora. The Docoglossa comprised representatives 
of both the suborders Abranchiata and Heterobranchiata, but 
all somewhat anomalous in their characters. It is in the 
first-mentioned order, however, that the richest results were 
obtained, since it appears necessary to separate the three 
species obtained into two genera, representing each a family, 
which differs by apparently sound characters from any hitherto 
known, and which it has therefore been necessary to describe 
as new. 
Almost all the species appear to be blind. 
Order RHIPHIDOGLOSSA. 
Family Cocculinide, Dall. 
Shell patelliform, not nacreous, symmetrical, with an entire 
non-sinuated margin, and a posteriorly inclined apex with a 
deciduous spiral nucleus. Muscular impression horseshoe- 
shaped, interrupted over the head. 
Animal with a prominent head and muzzle, two tentacles, 
as in Lepetide; gill single, plumose, asymmetrical, resem- 
bling that of Acmeide, extending between the under surface 
* Sci. Results of the Expl. of Alaska, i, art. ii. pp. 41-48 (1876), - 
