﻿SNAIL HOST OF ORIENTAL LUNG FLUKE — ABBOTT 81 



cavity is relatively short and round, although in preserved and 

 shrunken material it is apt to become folded. Two ovoid, horny jaws 

 are located on each side of the posterior region of the oral cavity. 

 They are hinged together at their dorsal edges by a thin, transparent, 

 hyaline sheath, which extends beyond the edges of the jaws slightly 

 laterally and posteriorly. The anterior edge of these brown jaws is 

 serrate. Small, polygonal platelets make up the anterior half of each 

 jaw. Tlie posterior region from which these platelets arise and are 

 pushed forward is translucent-gray and smooth. 



Just posterior to the jaws is found the large, bulbous buccal mass, 

 which contains the radula ribbon and the two salivary glands. If 

 the dorsal surface of the proboscis is slit open, the buccal mass is 

 readily observed. Within the various muscles and ventral to the buc- 

 cal cavity are found two pinkish, ovoid, translucent buccal cartilages. 

 They are connected dorsally by a transverse muscle. Tensor superior 

 muscles rise from the dorsolateral surfaces of the cartilages and run 

 forward and inward to attach themselves to the hyaline sheath or elas- 

 tic membrane of the radula ribbon. A number of other muscles, which 

 aid in the manipulation of the radula, are present. 



The salivary glands are two serpentine, thin-walled tubes, which 

 enter the buccal mass slightly to either side of the median line on the 

 dorsal surface. The glands coil posteriorly closely appressed to the 

 esophagus as far back as the central ganglia of the brain. The num- 

 ber and nature of these glands is similar to those found in Paludomus 

 (Seshaiya, 1934) and the Amnicolidae. Riech's (1937) observations 

 on Thiara scabra^ in which a dozen or so short salivary glands were 

 noted, are not in conformity with what has been found in other gas- 

 tropods in these families. 



The radula ribbon, which the animal rolls back and forth to rasp 

 at its food, is set in the center of the buccal mass. Its more highly 

 developed anterior end lies exposed on the bottom of the buccal cavity. 

 Posteriorly, where yet unused teeth are curled tightly together within 

 a protecting tubular sheath, the radula descends through the buccal 

 floor, runs slightly anterior within the buccal mass, and then turns 

 posteriorly once more to leave the buccal mass. This free end is the 

 swollen, rudimentary region where new teeth are being continually 

 formed and pushed forward. Underlying the anterior section of the 

 radula is a broad, winged hyaline sheath or elastic membrane, which 

 on its dorsal side serves as anchorage for the individual teeth, and 

 which on its ventral and lateral sides serves as a connecting base for 

 muscles. 



The radula is of the taenioglossate type, with the number of rows 

 from rudiment to leading edge varying in adults from 60 to 115, 

 although 85 to 95 appear most frequently. Each transverse row con- 

 sists of 7 teeth. In the center is the smallest, the central or rachidian 



