38 University of Michigan 
The jaw-plates and the radula (fig. 6) are almost identical 
with those cf A. flagellata belizensis C. and F., as figured by 
the authors (1890), although their figure of the jaw, in par- 
ticular, appears slightly idealized. Especially noteworthy are 
the small size and sharpness of the cusps of the central tooth 
and the broad and markedly double base of the second lateral. 
The latter is represented from a slightly different viewpoint 
in C. and F.’s figure of belizensis. In a few of the central 
teeth of the three specimens examined the first of the lateral 
cusps was double, and in many the outer cusp was double, so 
that in a few cases aS many as II cusps were found on a 
single tooth. A single inner lateral, in which the inner of the 
two small, outer cusps was divided, was also noted, while 
there was a quite constant tendency for a third cusp to be 
differentiated from the cutting edge outside of the other two. 
Ampullaria flagellata, subspecies erogata Crosse and Fischer 
(1890).—Thirty specimens. Ampullaria seems to have a 
peculiar ability to mature at almost any size. In places where 
the shells are abundant, specimens two centimeters in length 
have been seen in copulation. This was also noted in a Vene- 
zuelan species. These small shells may or may not assume | 
the adult characters, so that those that do have a thickened 
peristome and a quite different shape from those that do not. 
These small specimens are never markedly malleate, as the 
malleation is not well developed except in the older shells. 
The shells from the smaller, more temporary pools, espe- 
cially from those in the burnt-over areas (H, V, b), appear 
never to reach a large size, and thus form a quite well-marked, 
ecological subspecies, which appears to fit the description of 
A. erogata Crosse and Fischer very well. A. ceraswm Hanley 
is not very different, and may be a similar form, perhaps of 
another species. Examples of A. f. erogata measure: 
