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. PI. XIX. tig. 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 which, 

 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 Falmouth by Mr. Cocks 

 on Chorda lomentaria and Dumontia Jiliformis, 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 Plilebenterata, which, it will be recollected, is formed by 

 detaching the Eolididce from the other Nudibranchiata, and uni- 

 ting them with these to form a new order, founded upon the 

 gastric, or, according to that author's 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 

 Nudibranchiata, which appears to us to be a natural group, well- 

 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 out communication to the British Association we proposed the name 

 of Ictis 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. 



