62 BLOOMER : ANATOMY OF CERTAIN SPECIES OF SOI.ENIDAE. 



The anterior adductor muscle (fig. 6, A. A.) is a somewhat oval shaped 

 muscle, flattened dorsally, connected anteriorly with the mantle lobes, 

 and posteriorly with the dorsal integument, and by connective tissue with 

 the proximal portion of the foot. 



The posterior adductor muscle (fig. 6, P. A.) is a comparatively wide 

 and shallow muscle, connected anteriorly with the dorsal integument and 

 the pedis posterior retractor muscle, and posteriorly with the dorsal integu- 

 ment and the siphon. 



The retractor pedis anterior muscle, which is connected with the shell, 

 is very short and not bifurcated, while the retractor pedis posterior muscle 

 (fig. 6, P. A.) is very long, with long bifurcations, which are joined to the 

 posterior adductor muscle and the valves of the shell. 



As far as can be made out the alimentary canal has the appearance of 

 consisting of a short oesophagus, large stomach with the usual divisions, and 

 the caecum of the crystalline style and the first portion of the intestine 

 either possessing separate passages with the outside of the organs 

 joined together, or communicating with each other as in *S'. xtriijillatus and 

 dombeyi. 



Solen delerscoti, Chenm. 



aS\ tielerscoti is very short, the length being not more than three and a 

 half times the depth, and, judging from the specimens examined, a much 

 smaller animal than .S. cay ma — though it has the appearance of being com- 

 paratively largely built, with a large foot and siphon. It very closely re- 

 sembles S. vagina, differing from it in the shortness of the anterior part, 

 particularly the anterior adductor muscle, and the greater length of the pos- 

 terior part, iiK re especially the proximal portion of the siphon. The speci- 

 mens are not in a good state of presevation, but as far as can be seen of 

 the alimentary canal, the only noticeable point is that the crecum of the 

 crystalline style does not extend as far anterioriy along the pedal cavity. 



Solen (Solena) rudis, C. B. Adams 

 PI. x, figs. 7—9. 



External characters. — The specimen was removed from the shell before 

 being sent to me. The animal measures 7 cm. from the anterior end of 

 the mantle lobes to the poster 'or end of the posterior adductor muscle, and 21 

 millim. from the dorsal to the ventral surface It is nearly of a uniform 

 depth. 



The mantle lobes are concresced along their ventral surface. The 

 pedal aperture is situated at the anterior end and does not extend posteriorly, 

 either dorsally or ventrally. The periostracum is only attached to the 

 mantle lobes bordering the pedal aperture Inside the lobes are two 

 muscular flaps, which close the pedal aperture when necessary. There is 

 no fourth aperture. 



At the posterior end the mantle lobes form the proximal portion of the 



