I0I4- 
Colo AX. — Opisihohranch Fainia of Co. Dublin. 171 
round a one inch specimen of the Common Ascidi^\n, .4. 
mentula. Though usually a dull pink or red brown I ha\ e 
twice found coils of a clear yellow. The food of the x\plysia 
appears to consist chiefly of the smaller littoral sea weeds. 
The stomach contents of two large Skerries specimens kindly 
examined for me by Mr. A. D. Cotton, of Kew Herbariinn, 
were found to be made up for the most part of Polysi phoiiia 
viorcsceus and Ccramium riihrum. 
The radula of this species well illustrates the changes in 
form and numerical relations which that organ undergoes 
in the process of growth. Dissection of three indi\'iduals 
A, B, and C, respectively 12 mm., 38 mm., and 175 mm. in 
length (while alive and in motion) gave the following 
results : — 
A. B. C. 
Length of radula .. .. 2-5 mm, 5 mm. 0 mm. 
Dental formula .. .. 2txio-i-to 26 x 14-1 -14 4') x 17-1 -17 
In counting the lateral teeth the 3 or 4 simple plates 
forming the extreme outer members of the row were in all 
cases included. 
Along with these numerical changes a marked change 
took place in the form of the median tooth. In the youngest 
individual (A) the tooth was hollowed out by a deep posterior 
sinus or bay into which the denticulate central cusp of the 
tooth projected for its whole length. In the oldest indi- 
vidual (C) the bay had become almost obsolete by an increase 
of the basal portion of the tooth so that the central cusp 
altogether lost its prominence. These changes are in 
general agreement with those described and figured bv 
i\Ir. Walter Garstang in his " List of the Opisthobranchiate 
Mollusca found at Plymouth,*' ^- where he contends that 
A. dcpilaiis is but a luxuriant form of .-1. punctata. 
Pleurobranchus membranaceus (^lontagu). 
Rare. Dublin Bay: Kinahaii, '61. Portmarnock : ^-l^/^^^/zs, 
'78. One specimen 70 mm. in diameter dredged in 7 i. in 
Dalkey Sound, May, 1913 ; three specimens 35-45 mm. in 
1 Joiirn. of Marine Biol. Assoc., iSoo. 
A 4 
