404 Messrs. Alder and Hancock on a proposed New Order 
Genus Cenia*. 
Animal limaciform ; the back elevated ; head slightly angulated, 
and bearing two linear tentacles on the dorsal aspect, behind and 
exterior to which are the eyes. Anus a little behind the centre 
of the back. 
Cenia Cocksii, n. s. PL XIX. %. 1. 
Body robust, considerably elevated on the back ; black above, 
fading into fawn-colour at the sides. Head slightly angulated 
at the sides, and having a black central stripe, the sides of w hich, 
as well as the tentacles and the area surrounding the eyes, are 
yellow or fawn-coloured : on each side of the back, near the re- 
gion of the anus, is a slight ridge with three or four pale tuber- 
cular spots. Tentacles of moderate length, cylindrical and linear ; 
the points obtuse. Eyes very large. Length three-sixteenths 
of an inch. 
Two or three specimens were found at Palmouth by Mr. Cocks 
on Chorda lomentaria and Dumontia filiformis, in pools between 
tide-marks. 
We dedicate this species to its discoverer, whose exertions have 
added many species to the different departments of the British 
fauna. 
These animals have been placed by M. de Quatrefages in his 
order PhJehentei'ata, which, it will be recollected, is formed by 
detaching the Eolididce from the other Nudibranchiataj and uni- 
ting them with these to form a new^ order, founded upon the 
gastric, or, according to that authors views, the gastro-vascular 
system of organization. This order we have already objected to, 
both on account of our opinion of the incorrectness of the theory 
which the name involves, and because it breaks up the order 
Nudihranchmta, which appears to us to be a natural group, w’ell- 
distinguished by their external characters, and, though somewhat 
different in their internal anatomy, showing modifications, in that 
respect, so gradual that it is scarcely possible to draw a line of 
distinction which would separate them even into families. M. de 
Quatrefages seems now inclined to give up this group as an order, 
but thinks it convenient to retain it as a section of the Nudi- 
branchiata. We cannot, however, agree in any arrangement that 
would bring the Eolididce into closer relationship with these little 
animals than with the other families of the Nudibranchiata ; nor 
do we think that these animals can with propriety be referred to 
* In our communication to the British Association we proposed the name 
of Jctis for this genus, but having since found that this name is already ap- 
propriated to a genus of Mammalia, we have now changed it to Cenia, an 
ancient name of the place near which it was found. 
