300 Bulletin American Museum of Natural History [Vol. LITT 
1. Side teeth not more than usually elongate, the marginals being 
rather short: Lavigeria, Spekia, and perhaps Giraudia and Reymondia. 
2. Side teeth much lengthened, the two marginals nearly alike; 
the radula very small and weak (2 mm. long, 0.4 mm. wide in the large 
Paramelania damoni, Fig. 57). This group comprises all of the other 
genera, so far as known. | 
Radule similar to these two types are found in various other 
Melaniide. The second type is somewhat individualized by the shape 
of the lateral tooth, but still is not greatly unlike Melanoides. 
Fig.57 a-b, Teeth of Paramelania damoni (HE. A. Smith). At b a central 
tilted back to show full length of the cusps. 
Tiphobia, Bathanalia, and Lavigeria are viviparous, having the 
last part of the oviduct enlarged to form a brood pouch in the mantle, 
as in Melanoides and Viviparus. Tanganyicia has a genital groove on 
the side of the foot leading across to a brood pouch on the left side of 
the head, and is also viviparous. This seems to be a structure special to 
this very divergent genus. It is entirely analogous to the brood pouch 
of the Oriental region genus Antimelania Fischer and Crosse,! but, from 
its different position, apparently evolved independently. So far as is 
known, Limnotrochus, Paramelania and Spekia are oviparous. 
The series gives the impression that a few rather generalized types of 
Melaniide have been long isolated under highly favorable conditions, 
without much competition with gastropods of other families, and with 
ample time for adaptation into forms of shore and deep water and rock 
or mud bottoms. The shells of many genera show mature stages of 
1Type by present designation: Melania variabilis Benson. 
