190 Messrs. Alder and Hancock on new British species 



Cocks among a mass of sea-weed thrown u]) after a storm at the 

 mouth of Fahnouth harbour. Three specimens were obtained, 

 one of which Mr. Cocks kindly sent to us in spirits. The dis- 

 section of this specimen has shown a peculiar modification of the 

 digestive system which appears to have been overlooked by 

 Cuvier, and the particulars of which will appear in the 4th part 

 of our ' Monograph of the Nudibranchiate Mollusca.' 



Another species of great interest and beauty is apparently 

 new, and very nearly allied to oui* genus Proctonotus, but differs 

 from it principally in a peculiar crest-like body uniting the dorsal 

 tentacles. It probably belongs to the genus Janus of Veramy, 

 so far as we can judge from the notice of that genus inserted in 

 the Reports of Zoology lately published by the Ray Society ; but 

 whether or not this may be the case, which we have not the 

 means of verifying at present, the name of Janus being pre-occu- 

 pied in entomology, we propose now to describe it under the 

 generic name of Antiopa, and to characterize it as follows : — 



Genus Antiopa. 

 Bod]/ ovate, rather depressed and tapering to a point poste- 

 riorly. Tentacles four : the dorsal paii- linear, laminated, non- 

 retractile, and united near their base, for a short way up, by a 

 fleshy crest. Head anterior and inferior, without veil, but having 

 two short cylindrical oral tentacles. Jaws corneous. Branchia 

 papillose, elongated, clothing the sides of the back and extending 

 round in front of the head. Anus posterinr-dorsal, on the median 

 line. The digestive system supplied with two lateral trunks which 

 give off branches to the papillse. Common aperture of the gene- 

 rative organs on the right side. 



Antiopa splendida. 



Body of a transparent buff or lemon colour, and rather elon- 

 gated. Dorsal tentacles tapering and strongly laminated in an 

 oblique direction ; united below by an arched, semicircular la- 

 minated crest, which is placed longitudinally between them. 

 Branchiae very numerous, large and inflated, clothing the sides 

 of the back and passing round the front of the head. When held 

 erect they conceal nearly the whole of the body. They are ovate, 

 very transparent, of a pale buff-colour, and have a narrow, linear, 

 brown central vessel, which bifurcates at the top. The apex of 

 each papilla is of a brilliant opake bluish white with a metallic 

 lustre, deepening into ultramarine blue below. They are set in 

 about thirty transverse rows on each side uniting in front, each 

 row containing about five papillae ; the inner ones large and in- 

 flated, those next the foot small. The back is blotched with 

 metallic blue. Head subtriangular, the sides forming a kind of 



