380 



NERITIDiE. 



squarrosa, Recluz. 

 subgranosa, Soiv. 

 subpunctata, Recluz. 

 triserialis, Sow. 



Tritoniensis, Le Guillou. 

 Troschelii, Recluz. 

 unidentata, Recluz. 



Genus CATILLUS, Humphrey. 



Head large ; foot attached on each side to the 

 visceral mass, forming a cavity open behind. 



Operculum small, thin, rudimentary, calcareous, qua- 

 drilateral, surface radiated, with a subulate tooth at the 

 hinder edge, the other edges sharp and thin. 



Shell ovate, depressed, patelloid, covered with an 

 epidermis; apex nonspiral, nearly symmetrical, re- 

 flexed posteriorly ; aperture very large ; inner lip sep- 

 tiform, margin simple, sharp, edentulate. 



S?/n. Cimber, Mont/. Navicella, Lam. Cibota, 

 Brown. 



Ex. C. lineatus, Lamarck, pi. 42, fig. 4. Opercu- 

 lum, C. porcellanus, Linnaeus, fig. 4, a, 4, h. Shell, 

 C. porcellanus, fig. 4, c. 



The operculum in this genus is applied to the dorsal 

 surface of the foot, and is concealed in the cavity 

 which it forms with the visceral mass. In Catillus 

 proper the apex is entirely posterior, often eroded, 

 and distinct from the hind margin. The species are 

 usually found on the banks of rivers adhering to floating 

 sticks and to the petioles and roots of the Nipah palms 

 and other plants that live near rivers ; they are also 

 found attached to smooth stones. Their principal loca- 

 lities are the Philippines, New Holland, New Guinea, 

 the Feejees, New Ireland, and the Mauritius and adjacent 



