Mr. Alder and Mr. Hancock on new Mollusca. 31 



inches, lines. 



Lengtli of anal 1 B 



caudal 2 9 



Height of tallest dorsal spine (4th) 1 4 



second spine 1 1 



tenth dorsal spine 9A 



soft dorsal 1 1 



anal 1 4 



third anal spine 8 



Length of space between anus and anal fin 9| 



anal and caudal 1 9 



dorsal and caudal 1 1 



Height of head at nape 3 4 



[To be continued.] 



IV. — Descriptions of several new species of Nudibranchous 

 Molluscafound on the coast ofNortliumherland. By Joshua 

 Alder, Esq., and Albany Hancock, Esq. 



During two short periods of residence at Cullercoats last 

 summer, we devoted some leisure time to an examination of 

 the Nudibranchous Mollusca of the coast, for the purpose of 

 ascertaining the number of indigenous species, and of ob- 

 serving the habits and oeconomy of these little-known ani- 

 mals. In the former respect our success was beyond our 

 most sanguine expectations. Although our researches were 

 confined to a very small portion of the coast, not exceeding 

 two or three miles, in the immediate neighbourhood of Cul- 

 lercoats, and without the assistance of a dredge in collecting 

 the deep-water kinds, we succeeded in obtaining thirty-four 

 species, a number nearly equal to what has yet been recorded 

 as inhabiting the whole of the British seas. Of this number 

 about one half are entirely new. Careful drawings of the 

 whole have been made while in a living state, which, together 

 with more full descriptions than are now offered, may be given 

 to the public at some future time, when further investigation 

 shall have enabled us to clear up some points in their history 

 of which Ave are at present in doubt, and perhaps to increase 

 the list by the discovery of additional species. In the mean 

 time we take the liberty of sending for insertion in the ' An- 

 nals' short characters of seventeen species which appear to be 

 undescribed. 



The most interesting point of physiology that we have ob- 

 served in this tribe is the existence of eyes in T>oris and Go- 

 niodoris, genera that have hitherto been described as entirely 

 devoid of these organs ; they can be most distinctly observed 

 in young individuals, where the skin is very transparent. In 

 this state we have succeeded in detecting them in Dot-is re- 

 panda and Goniodoris nodosa, situate behind the dorsal ten- 



