PLATE IX. 



!2. — Alimentary canal opened along the dorsal side. Natural size. 

 AP, anterior prelingual process. 

 BM, buccal membrane. 

 C, coecum, showing its projecting lamellae. 

 HP, openings of the hepatic ducts into the coecum. 

 LJ, lower jaw. 

 MM, mandibular muscle. 

 Oe, oesophagus. 



l'P, posterior prelingual process. 

 Pr, proventriculus. 

 R, radula. 

 Be, rectum. 



S, saccular posterior portion of the stomach. 

 S( >, salivary pore. 

 SI', salivary process. 

 T, tentacles of the stomach. 

 Tn, tongue. 

 U.T, upper jaw. 

 V, vestibule. 

 X, apparently permanent ridges of the oesophagus. 



1, 1, intestinal ridge. 



2, intestinal ridge. 

 ."., :;, intestinal I 



4, foliaceous ridge. 

 Fig. :!:!. —Ventral view of the buccal mass, a portion of its muscular membrane h:t\ ing been folded back. X 2. 

 BO, buccal ganglion. 



BM, buccal membrane, cut ami turned forward over the tip of the jaw. 

 LJ, outer flange of the lower jaw". 

 I,M, levator muscle of the buccal mass. 



M, mandibular muscle; this ends ventrally along lh lge of the upper jaw. 



MM, muscular membrane of the buccal mass. 



N 1 , outer cerebro-buccal connective. 



N 2 , inner cerebro-buccal connective. 



Oe. M, membrane surrounding the base of the oesophagus ami connecting with the membrane surrounding 



the central nervous system. 

 (IM, part of the membrane stretched between the ventral buccal retractors. 

 I'h. ( i, pharyngeal ganglion. 

 RL, ligament of the radularsac. 

 RS, radular sac. 



VBR, ventral buccal retractor muscle. 

 I, retractor of the anterior prelingual process. 

 1', retractor of the posterior prelingual process. 

 :i, :-;, unpaired muscle, forked posteriorly, going to the posterior prelingual process. 



4, muscle extending into the posterior prelingual process, ami also to the portion of the tongue anterior to the 



upwardly directed part of the radular sac. 



5, muscle to the anterior portion of the tongue. 



6, muscle to the membrane covering the projection of the upper jaw . 



7, muscle to the dorsal surface of the radular sac. 



s. Muscle which probably plays a share, at least, in the opening of the jaws. 

 ',i, oi'i^iiis of muscles 1, 2, 7, upon the inner surface of the muscular membrane. 



Fio. 3-1. — Dorsal view of the buccal mass, tl nveloping muscular membrane having been cut along the median line. 



The view is also somewhat from behind. 2. 



A, I nacelles of the superioi mandibular artery penetrating the mandibular muscles. 

 BM, buccal membrane, also slit open dorsally. 

 LJ, tip of lower jaw. 

 M, mandibular muscle. 



muscular membrane of the buccal mass. 



Oe, oesophagus, swollen at one place by food which remained in il when the animal died. 

 I'.I, tip of the upper jaw. 



C.T, posterior edge of the inner flange of the upper jaw . 

 1' iG. 35. -The radular sac and the lingual muscles of one side exposed and viewed from the ventral side. \ 2. 

 EL, external lingual muscle. 

 I'd.', cut end of the external lingual muscle. 

 I I .. internal lingual muscle. 

 LP, lingual protractor muscle. 

 R, radular muscle. 

 I;' cut end of the radular muscle. 

 Ra, radula. 

 RS, radular sac. 

 S, septum extending from the dorsal median line of the tongue to the muscular membrane just above the 



radular sac, which has been cut aw a;, from the exposed side of the preparation. 

 T, tendinous area where the lingual muscles join. 

 X, division of the septum. 

 Y, point of the upper jaw to which the lingual protractoris attached. 



