100 JOSEPHINE RANDALL AND HAROLD 1 1 LATH. 



As noted in a preceding paragraph, the mouth opening is 

 borne on the summit of a low papilla in the mid line. In entire 

 specimens it is further distinguished from tin- opening into the 

 pseudopallium by occupying the center of a whitish area, up- 

 wards of 3 mm. in diameter in the largest specimens, canard by 

 the compact feltwork of circular and radiating muscles enveloping 

 what probably corresponds to the buccal tube. In the immediate 

 neighborhood of the mouth opening the canal is comparatively 

 slender, 0.28 mm. in diameter in large individuals, and is pro- 

 vided with a lining of simple columnar cells whose distal portions 

 contain small quantities of a faintly staining, vacuolated secre- 

 tion. Behind this point large numbers of small, irregularly dis- 

 tributed pyriform gland cells appear imbedded in the muscular 

 meshwork surrounding the digestive tract, and their darkly 

 staining ductules may be traced to intercellular openings in the 

 buccal or pharyngeal epithelium, whose extent is increased by two 

 symmetrically placed diverticula with short, stubby branches 

 (PI. I., Fig. 2) extending a short distance into the surrounding 

 muscle sheath. These paired glands probably correspond to the 

 ventral salivary glands of other molluscs as the buccal ganglia, 

 connected by a commissure, are located in their vicinity. 



No trace of a radula exists. 



The buccal-pharyngeal tube with its enveloping glands and 

 muscles, is relatively short, probably not over I mm. in length, 

 but it spans a well defined head cavity (PI. II., Fig. 3), which is a 

 portion of the h?emocele as in other molluscs. Curving gently 

 toward the ventral side of the body the tube leaves the sinus, 

 and now devoid of gland cells and with a comparatively thin 

 sheath of longitudinal and circular muscles, it passes back a 

 short distance into the body and unites with the main portion of 

 the digestive tract (/), a spacious cavity, lined with glandular 

 epithelium, occupying most of the visceral mass not held by the 

 gonad and its duct. 



The pericardial cavity (Tl. I., Fig. 2) is situated on the anterior 

 surface- of the visceral mass on the right side. The contained 

 heart consists of a single auricle and ventricle, both of large size 

 and highly muscular. The first-named receives the blood from ,1 

 broad sinus, which on one hand passes from the liver surface 



