TETHYS DACTYLOMELA (RANG) 21 



in general with those here given. Eliot, in his "Notes on Tecti- 

 branchs and Naked Mollusks from Samoa," Proc. Philadelphia 

 Academy, 1899, p. 515, states that the radula of a Tethys dacty- 

 lomela examined by him possessed a unicuspid central tooth, the 

 laterals having an inner, but no outer cusp, a condition decidedly 

 different from that described above in the specimens which I have 

 examined. 



Salivary glands. The ducts of the salivary glands emerge 

 from the buccal mass on its posterior surface on either side of the 

 anterior end of the esophagus. The glands are long flattened 

 strap-shaped structures, 1.5 mm. in greatest width. They pass 

 through the esophageal collar formed by the central nervous 

 system, extend backward along the left side of the visceral mass, 

 the left one above, and dwindle away posteriorly, their tips be- 

 ing attached to the sides of the anterior portion of the first 

 triturating stomach, the tip of the left one being situated dorsally, 

 that of the right one ventrally. 



Esophagus and stomach. The esophagus is a short broad 

 thin-walled tube about 6.5 mm. in length, dilating posteriorly 

 into the capacious stomach. Its inner surface is smooth, save for 

 a few low longitudinal ridges. In the stomach may be dis- 

 tinguished three divisions. The first, or ingluvies, is everywhere 

 very thin walled, its inner surface is smooth and passes gradually 

 into that of the esophagus in front. In all the specimens exam- 

 ined the ingluvies was greatly distended with fragments of algae. 

 In its lower posterior portion the ingluvies suddenly constricts 

 into the "first triturating stomach" of Mazzarelli, clearly marked 

 externally by its strong muscular wall, the fibres of which are 

 mainly arranged in a circular direction. The width of this band 

 varies from n.o mm. to 18.0 mm. in the specimens examined, 

 the diameter of the contracted stomach at this point ranging from 

 15.0 mm. to 20.0 mm. Borne upon the inner surface of this wall 

 is a series of strong horny pyramidal teeth of a light amber 

 color. The sides of these teeth are formed by four roughly 

 triangular faces, and, the two anterior ones being larger than 

 the two posterior ones, the tip of the tooth is, in consequence, 

 inclined backward. The teeth are borne upon plate-like eleva- 

 tions of the epithelium, corresponding in shape to the bases of 

 the teeth. In alcoholic material the teeth are readily separable 



