﻿86 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 102 



the outer surface of which it forms an S-shaped coil. Beyond this the 

 intestine becomes thin walled and transparent. The long, round feces 

 become packed in oblique rows as they pass toward the anus. The 

 last section of the intestine is welded to the right side of the mantle. 

 When feces pass from the small, round anus, they usually drop down 

 the right side of the body. Their passing is facilitated by a shallow, 

 ciliated gi-oove, running from the region of the birth pore obliquely 

 forward and downward toward the edge of the foot. 



NERVOUS SYSTEM 

 Figure 37 



The central ganglia of the nervous system are concentrated in the 

 head region a little behind the proboscis. They may be reached easily 

 by slitting open the dorsal side of the proboscis and head. The 

 esophagus runs directly through the group, as described previously. 

 The brood pouch borders the posterior regions of these gajiglia 

 remarkably closely, and on more than one occasion young snails have 

 been found within 0.5 mm. of the central ganglia. The two large pedal 

 ganglia are more difficult to reach, for they are set deeply in the fore 

 regions of the foot directly below the other ganglia. 



The central ganglia have a thick dorsal covering of connective tissue. 

 The surfaces of these ganglia are colored a deep maroon in living 

 specimens. In preserved material the color is waxy white. They are 

 oval, with thicker and more rounded posterior ends, and with tapering, 

 dorsoventrally flattened anterior ends, which give rise to six small 

 nerves. The two ganglia are united by a very short, thick commissure. 

 The number and size of the anterior nerves may vary, although the 

 more important ocular and tentacular nerves, which are the most 

 laterally placed, are constant. The inner four or five nerves run 



Figure 36. — Alimentary system: A, Dorsal view of buccal mass (semidlagrammatic) 

 (BS, buccal sac; LC, left central ganglion; MO, mouth; OE, esophagus; RM, retractor 

 muscle; SG, salivary gland). B, Sagittal section of esophagus (MO, mouth; OE, esoph- 

 agus; SG, left salivary gland). C, Crystalline style; top figure from preserved specimen; 

 bottom figure from life. D, Semidlagrammatic view of entire alimentary system (AN, 

 anus; DD, digestive ducts coming from digestive gland; FE, feces in intestine; IN, intes- 

 tine; OE, esophagus; RE, rectum or lower intestine; SS, lower stomach or crystalline 

 style sac; ST, stomach). E, Dorsal view of esophagus as it passes posteriorly from 

 beneath the edge of the brood pouch (LM, longitudinal muscles; OE, esophagus); PO, 

 brood pouch. F, Left lateral view of stomach (IN, intestine; OE, esophagus; SS, crys- 

 talline style sac; ST, upper stomach). G, Interior of stomach; top left and bottom left, 

 cross-sections; right figure, longitudinal section (CC, central column; CS, entrance of 

 crystalline style sac; DD, ducts to and from digestive gland; HY, hyaline sheath sur- 

 rounding style; IN, intestine; OE, esophagus; OS, outer wall of crystalline style sac; 

 PIj, plicae of stomach wall; SL, lumen of stomach). 



