MB. G. E. DOBSOS OS APLYSIA. DACTYLOMELA.. 159 



Notes on Aplasia dactylomela. 

 By Gk E. Dobson, M.A., M.B., P.L.S., &o. 



[Read June 17, 1830.] 



The specimen which forms the subject of the following notes was 

 obtained by Mr. E. Yacy Ash, MB., Surgeon, Army Medical 

 Department, in February last, at Bermuda. It agrees so closely 

 in size, and in the coloration and shape of the body and shell, with 

 the figures and description given by Eang of his Aplysia dactylo- 

 mela*, from the Cape-Verd Islands, that I have little hesitation 

 in recognizing it as an example of that species, though from the 

 opposite side of the Atlantic. 



The specimen in question was found in shallow water inside 

 the reef fringing the island, and was seen through the clear water 

 moving along on the bottom, the lateral swimming-lobes keeping 

 up a gentle undulatory motion. Mr. Ash describes its colour as 

 a rich drab, marked all over with circles and streaks of velvet- 

 black, the latter most abundant on the mantle covering the shell 

 and on the lateral swimming-lobes. The shell agrees in all re- 

 spects with that of A. dactylomela as figured by Eang, and the 

 only difference observable is that the margins of the swimming- 

 lobes are not tinged with violet. This might be accounted for 

 by supposing that such a fugitive colour had disappeared in the 

 alcohol, but the captor does not remember to have seen it in the 

 living animal. 



The following points appear not to have been previously 

 noted : — 



The lingual ribbon is nearly as wide as long, and supports 

 about 75 rows of recurved teeth, having the formula 43-1-43, re- 

 presenting the number in a row taken at the widest part. 



In fig. 1, where portions of two tooth-rows from the centre 

 of the lingual ribbon are shown, the median or rhachidian 

 tooth is smaller than the lateral teeth, and has a blunt central 

 cusp with two small lateral cusps. The bluntness of the central 

 cusp may, however, be due to wear, although throughout the 75 

 rows this cusp presents the same character. It may also be ob- 

 served that the first teeth to left and right of the median tooth 

 are not symmetrically developed, the left tooth being much larger 



* Eang, ' Histoire Naturelle des Aplysiens,' p. 56, pi. ix. (1828). 



