NOTES ON SOME BRITISH NUDIBRANCHS. 343 



side, the ganglia appear united in a horseshoe-shaped mass in which no 

 divisions are clearly distinguished. Seen from below, the division 

 between the cerebro-pleural and pedal ganglia is plain, but the cerebro- 

 pleural ganglia are not distinctly divided into two portions. The 

 common commissure is thick and very short. 



The integuments, especially the tuberculate dorsal surface, are very 

 spiculous, and contain a dense mass of colourless rods, often slightly 

 bent, but not swollen in the middle, jointed, or branched. 



No labial armature could be found, but on the labial cuticle in some 

 specimens were granular markings resembling grey dust, but not form- 

 ing rods or compact plates. The radula consists of about thirty rows, 

 and the number of teeth on each side of the rhachis does not appear to 

 much exceed forty as a maximum; but the whole radula is fragile and 

 difficult to extend. The teeth are transparent and colourless, longer 

 and thinner than in A. taherculata, and with narrower bases. Near the 

 rhachis (Fig. 2. a. b.) the teeth are low and with comparatively broad 

 bases ; but they increase in length and slenderness towards the outside 

 until the last two or three, which are shorter, but often somewhat 

 deformed (Fig. 2. f.). Teeth with abnormal lumps and projections 

 occur in all parts of the radula (Fig. 2. d.). 



The oesophagus is narrow at first, but widens and enters the liver. 

 The stomach lies within the liver. The gall bladder is small and pear- 

 shaped. The intestine issues from the liver about the middle of its 

 dorsal surface, runs forward and then turns backward. The liver is of 

 a dull orange colour; the hermaphrodite gland, spread over it, is of a 

 dull opaque white. 



The spermatotheca is large, greenish or bluish grey, and spherical. 

 The spermatocyst is small, white or orange-white, less distinctly 

 spherical, and sometimes pear-shaped. There is no prostate. The vas 

 deferens is very slender, long, and convoluted. The penis small, conical, 

 and unarmed. The duct seems to issue at the side of the tip. 



Though this species is commonly confused with A. tuherculata, it 

 seems to differ in the following points : — 



(1) The typical coloration is different, though it is very often imper- 

 fectly developed. 13ut there are nearly always purple spots on the 

 lower side of the mantle, which seem not to occur in A. tuberculata. 



(2) The general form is flatter. 



(3) The shape of the tentacles and anterior part of the foot is 

 markedly diO'erent. 



(4) The tubercles are less prominent and of more equal size. 



(5) The branchiie are stouter and less voluminous. 



(6) The shape of the teeth is dilferent. 



(7) The stomach is enclosed within the liver. 



