404 Messrs. Alder and Hancoek on a proposed New Order 



Genus Cenia*. 



Animal limaciforra ; 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. fig. 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. JEyes very large. Length three-sixteenth* 

 of an inch. 



Two or three specimens were found at Falmouth 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 Phlebentei'ata, 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, agi'ce in any arrangement that 

 would bring the EoUdidce into closer relationship with these little 

 animals than with the other famihes of the Nudibranchiata ; nwr 

 do we think that these animals can with propriety be referred to 



* In our communication to the British Association vre proposed the name 



n^ Ictis for this geriiis, but having since found tliat this name is aheady ap- 

 propriated to a genuB of Mam m alia, we have now changed it to Cenia, an 

 ancient name of the place near which it was found. 



