BLOOMER : ANATOMY OP PHARELLA AND TAGELUS. 119 



out dorsally and ventrally, extend in a deep semi-circular direction, 

 forming large surfaces from which they adhere to the valves of the shell. 



The anterior adductor muscle (Fig. 4, A. A.) is a plate of muscles of 

 greater length than depth, and divided into two unequal parts by the 

 ventral integument passing between them to the dorsal surface. Anteriorly 

 the muscle is connected with the mantle lobes, and posteriorly with the 

 pedal and the dorsal integument. 



The posterior adductor (Fig. 4, P. A.) muscle is a deep plate of muscles 

 flattened anteriorly, and from this side is joined with the bifurcated parts 

 of the retractor pedis posterior muscle and dorsal integument, and at the 

 posterior side with the proximal portion of the siphon, the dorsal integument 

 and the mantle lobes. 



The pedis retractor anterior muscles (Fig. 4, P.R.A.) run ventrally, 

 apparently over the longitudinal pedal muscles. There is no bifurcation 

 of their free parts. 



The pedis retractor posterior muscle (Fig. 4, P.R.P.) is very narrow 

 and of considerable length, the posterior parts of the bifurcated portions 

 being connected with the posterior adductor muscle. 



From the specimen examined it was not possible to trace the pedis 

 elevator or branchial retractor muscles, present in S. strigillatus. 



Alimentary Canal. 



The lips (Figs. 5 and 6, A.L. and P.L.) formed by the junction of the 

 labial palps, point anteriorly. The oesophagus (Figs. 5 and 6, Oe.) is very 

 short, it passes posteriorly and soon opens into the stomach. In shape 

 the stomach (Fig. 4, St.), though similar to that of S. strigillatus, ''' is 

 longer, shallower, and the divisions are not so pronounced. I have, 

 however, used the same terminology for the respective divisions. In 

 the left part of the stomach and anterior to the centre lies the central 

 division (Fig. 5, CD.), bordered by a muscular ridge (Fig. 5, C.D.R.), 

 which on its dorsal side is developed into a muscular papilla (Fig. 5, M.P.). 

 From this central ridge, proceeds another one (Figs. 5 and 6, A.D.R.) 

 which separates the dorso-central from the anterior division, then passing 

 around the stomach in an irregular manner, divides the anterior from the 

 posterior division. 



The anterior (Figs. 5 and 6, A.D. St.) is larger than the posterior 

 division (Figs. 5 and 6, P.D. St.), and its dorsal surface consists of a very 

 muscular layer. The dorso-central division (Fig. 5, D.D.) is shallower 

 and not so readily distinguished. The posterior division (Figs. 5 and 6, 

 P.D. St.) is larger, depressed dorsally, and deeper at the posterior end. 



From its ventral surface proceeds the caecum of the crystalline style 

 (Figs. 5 and 6, C.C), which goes ventrally, then curving terminates near 

 the dorsal surface of the pedal cavity. As in *S. strigillatus the intestine 



3. Joum.M^lac, 1903, vol.x, p. 36, 



