MOLLUSCA FROM INDIANA AND OHIO 449 



Planorbidae 



Planorhis campanulatus Say. A dozen specimens of this species, 

 mostly mature, occurred in the material examined. The adults 

 are of normal size and typical form. 



Planorhis antrosus Conrad. A fairly abundant species of large- 

 sized individuals, mostly mature. There is considerable variation 

 among the specimens, especially in the shape of the aperture, 

 which has a tendency to become bell-shaped. A number of 

 individuals approach variety aroostookensis Pilsbry, and one 

 specimen would certainly be called variety portagensis Baker, if 

 found in Maine. Several specimens have a number of rounded 

 ridges on the body whorl near the aperture; these indicate the 

 location of former apertures. 



Planorhis antrosus striatus Baker. About 10 per cent of the 

 antrosus may be referred to this variety with strong spiral striation. 

 This is very strongly marked in the majority of the fossils of this 

 deposit. 



Planorhis altissimus Baker. This small Planorhis, first described 

 from marl deposits at Urbana, Illinois, proves to be widely distrib- 

 uted and to be the common Planorhis of the parvus group in the 

 marl deposits. It is very variable, only a small percentage being 

 typical as figured in the original description (Baker, 1918, p. 94). 

 The aperture varies from rounded to elliptical and may be deflected 

 to a marked degree or placed in an almost continuous line with the 

 body whorl. In all specimens examined, however, the upper part 

 of the aperture forms a distinct shoulder and the whorls are more 

 or tess flat-sided, features not found in true parvus, which is nor- 

 mally a smaller shell. AUissimusis, after Amnicola lustrica and A. 

 winkleyi leightoni, is the most abundant shell in this deposit. 



Planorhis deflectus Say. Three adult individuals of this small 

 Planorhis were found in the material examined. The peripheral 

 keel is very marked in these specimens, and the aperture varies in 

 the degree of deflection, in one specimen being almost basal. The 

 largest individual measures 6 . 5 mm. in greatest diameter. 



Planorhis hirsutus Gould. A single specimen seems referable 

 to this species, having the less conspicuous keeled periphery and 

 rounded whorls of hirsutus from Massachusetts. This species 

 seems quite separable from deflectus. 



