bloomer: anatomy of pharella and tagelus. 115 



Musculature. 



i. The Pallial Muscles (Fig. 1, P.M.). — These form a deep band 

 round each mantle lobe, and ventrally lie chiefly at right angles to the 

 pallial edge. They obtain their maximum thickness at the line of adhesion 

 to the valves of the shell. At the posterior end they form the proximal 

 siphonal portion and are much more strongly developed (Fig. 1). 



The anterior adductor muscle (Fig. 1, A. A.) is a large and nearly 

 circular muscular plate, pined dorsally and anteriorly with the dorsal 

 integument and mantle lobes, and posteriorly with the foot by the mus- 

 cular ventral integument. 



The posterior adductor muscle (Fig. 1, P. A.) is a large and deep plate 

 of muscles, curving anteriorly and posteriorly towards the flattened dorsal 

 surface. Anteriorly it is connected with the retractor pedis posterior 

 muscle, and posteriorly with the proximal portion of the siphon and the 

 dorsal integument. 



a. The Pedal Muscles. — The muscular arrangement of the foot is 

 similar to that of Sohn and is strongly developed. The three kinds of 

 muscles found in this genus are also present, but in Pharella orientalis 

 there is a large increase in the number of rows of the transverse muscles. 

 Briefly, on each lateral side are two groups of longitudinal muscles, and 

 between these there is a semi-circular band passing from the dorsal to the 

 ventral surface. Between the two inner and much larger layers of longi- 

 tudinal muscles, are a nuinber of rows of transverse muscles, the fibres 

 of which pass through the longitudinal muscles to the semi-circular layers, 

 and they either continue, or other muscular fibres pass from these latter 

 through the outer longitudinal bundles to the muscular pedal integument. 



The pedis retractor anterior muscles (Fig. 1, P.R.A.) are short and 

 thick, and in the foot proceed mostly in a posterio-ventral direction over 

 instead of under the longitudinal pedal muscles. There does not appear 

 to be any bifurcation of the free portions. 



The pedis retractor posterior muscle (Fig. 1, P. P.P.) is a comparatively 

 long muscle, narrow at the sides and increasing in depth towards the 

 median line. The bifurcated parts are short and connected with the 

 posterior adductor muscle. Anteriorly the muscle continues as a portion 

 of the longitudinal muscles of the foot. 



Alimentary Canal. 



The lips (Figs. 1, 2 and 3, A.L. and P.L.) formed by the union of 

 the labial palps are wide, especially the upper or anterior one, wliich is 

 of considerable width. The oesophagus (Figs. 2 and 3, Oe.) first runs a 

 little dorsally, then turns posteriorly and opens into the stomach. 



The stomach (Fig. 1, St.) is a long and irregularly shaped sac, con- 

 sisting of a number of divisions which, for convenience, I have termed 

 Anterior-oesophagael, Posterior-oesophagael, Cardiac, Central, and Pyloric. 



