36 BLOOMER : ANATOMY OF CERATISOLEN AND SOLECURTUS. 



A-ttaclied to tlie sliell between each of the elevator pedis and siphonal 

 retractor muscles is a long and narrow muscle, which is connected with 

 the muscular tissue running along the base of the g'lls, and evidently 

 acting as a branchial retractor muscle for the purpose of folding the gills 

 into a close mass when the proximal portion of the siphon is contracted. 



Alimentary Ganal. 



The mouth (Figs. 5 & (J, J/.), a transverse opening of the ventral 

 integument, is situated under the posterior })ortion of the anterior ad- 

 ductor muscle, and between it and the foot. The li})S (Figs. 5 and G, 

 A. L. and 1'. L.), formed by the junction of the labial palps, project for- 

 A\ardl\-. 



The oesophagus (Figs. 5 c^: G, Ue.) is narrow, of medium length, and 

 proceeds posteriorly to the stomach. 



The stomach (Figs. -1. 5 and G, -S7.) is an irregularly-shaped sac, con- 

 taining a nundjer of divisions. This applies particularly to the left side, 

 which is divided into four parts by muscular ridges. For convenience, 1 w ill 

 call the divisions Anterior, Posterior, Central, and Dorso-central. Towards 

 the centre of the left half is an oval muscular ridge (Fig. 5, C. D. R.) com- 

 pletely bordering a deep cavity — the central division (Fig. 5, C. D.). The 

 lumen soon spreads out, and extends a considerable distance anteriorly and 

 posteriorly. On the dorsal side, and continuous with this ridge, is a 

 slighter one (Kigs. 4 and 5, A. D. R.) passing iiloug tlie dorsal surface of 

 the stomach down tlie right side, and returning al(jng the ventral surface 

 in a more pronounced degree, and joining the ventral side of the ridge of the 

 central division, thus separating the anterior division from the posterior 

 portion of the stomach. The posterio-dorsal part of the ridge of the central 

 division is developed into a muscular papilla (Fig. 5, M. P.). From the 

 posterior side of the base of the papilla runs another muscular ridge (Fig. 

 5, P. St. li). which first separates the dorso-central from the posterior 

 division, and then passes along the dorsal surface in a posterior direction 

 towards tlie median line, and disappears. The Dorso-central division 

 (Fig. 5, D. I).) is smaller, but of considerable depth, and lies abov(" the 

 muscular papilla. The Posterior division (Fig. 5, P. St.) is very large. 

 The ventral portion, after narrowing, forms the opening of the caecimi of 

 the crystalline style (Fig. 5, C.C.) and intestine (Kig. 5, In.). The caecum 

 of the crystalline style is a large and long sac, ])a,ssing firyt in a ventral 

 direction, then gradually curving, terminates near the dorsal surface of 

 the pedal cavity. When the caecum and the intestine leave the stomach, 

 the intestine (Fig. 4, In.) on the right anterior side of the caecum, they 

 are only partly divided from each other, the intestine being small and 

 appearing as a narrow, deep, and irregular groove on the side of the 

 caecum. At the distal end of the caecum the intestine becomes quite 

 separate, and the typhlosole cuunnences, formed by the invagination of a 



