BLOOMER : ANATOMY OF CERATISOLEN AND SULECURTUS. 33 



m a hilohed anus (Fig. 1, A.). As previously uientioned, the anus is situ- 

 ated more posteriorly than in S. ensis. 



The liver (Fig. 1, L) is situated as in *S'. ensis over the fore-pai't of 

 the stomach, and passes for a short distance over the anterior adductor 

 muscle, and posteriorly under the stomach as far as where the intestine 

 leaves it. 



Nervous System. 



The nervous system, like that of S. pellucidus, differs from -S'. ensis in 

 the number of the pallial nerves. Each anterior pallial nerve gives rise 

 to one branch only, which leaves the main nerve just after it reaches the 

 anterior adductor muscle, and crosses the mantle lobe, then divides, the 

 two parts joining the circumpallial nerve. 



The posterior pallial nerve d(jes not give rise to any branch which 

 crosses the mantle lobe as in ^S'. ensis. 



There is only one circumpallial nerve. 



Circulatory System. 

 This is the same as in S. ensis, excepting in a few minor details. 



Soleeurtus strigillatus, L. 



External Characters. 



The mantle lobes are comparatively short and wide. They project 

 separately some little distance anteriorly from the dorsal surface of the 

 ii.nterior adductor muscle, and in a semi-circular curve form the pedal 

 aperture ; while posteriorly they are broader, and from a position 

 above the posterior adductor muscle run with a slighter curve 

 laterally. In the anterior part of the mantle lobe the muscles 

 of the pallial edge are wide and thick, but they gradually diniinish in Avidth 

 towards the posterior end. The pedal aperture, lying ventrally, extends 

 in a dorso-posterior direction, and on each mantle lobe is bordered by a 

 muscular Hap. The mantle lobes are connected ventrally with each other 

 by a wide piece of muscidar tissue, which posteriorly is continuous with 

 the 2)roximal portion of the inhalent si phonal chamber. Dorsally the 

 proximal portion of the siphon is for some distance from tbe median line 

 connected with the mantle lobes and the dorsal integument ; while the 

 muscles, chiefly from the lateral portion of it, pass under the mantle lobes 

 and afterwards through them in large and powerful siphonal retractor 

 muscles, and are attached to the valves of the shell. 



The external surface of the muscular tissue connecting the ventral 

 portions of the mantle lobes, the free edges of the mantle lobes, and the 

 proximal portions of the siphonal chambers are coloured a mottled brown, 

 but the brown colour of the free portions of the siphon is of a more con- 

 sistent nature. This colouring, however, appears to be subject to variation, 

 and some specimens are nearly white. 



