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LYMNZIDA OF NORTH AMERICA. 26 
it joins the parietal wall is somewhat abruptly curved in. The colu- 
mella is also straighter than in humilis, These distinctions hold good 
in the presence of the rather large series of humilis examined. Some 
specimens of modicella, however, closely approach humilis, especially 
in the form of the inner lip, which sometimes wholly lacks the peculiar 
compression at its junction with the parietal wall. (See plate XXIX, 
fig. 35; pl. XXXI, fig. 4.) The South Carolina specimens of humilis 
also vary in this respect. (Compare the figures on plate DOL) ackhic 
rounder aperture, more obese body whorl and broadly conic spire of 
humilis appear, however, to be constant. Modicella may be distin- 
guished as a race occupying the whole of the United States except 
the southeastern states bordering the Atlantic Ocean and the Gulf of 
Mexico. Some forms of Galba bulimoides cassi somewhat resemble 
modicella, but may be distinguished by the form of the inner lip. 
Parva and sterkii also differ in the form of the inner lip. Obrussa 
has a differently shaped aperture and the inner lip is notably com- 
pressed and bent inward at its junction with the parietal wall. Galbana 
is similar in some of its forms, but is typically shorter, more corpulent 
and with a more depressed spire, more shouldered whorls and a rounder 
aperture. Young specimens of Galba bulimoides from California 
have been mistaken for modicella. A form of modicella occurs 
at La Porte, Indiana, which has a strongly zebra-marked shell, the 
narrow white stripes standing out vividly against the dark brown back- 
ground. As many as fourteen stripes may be counted on the last whorl 
of one specimen. 
The spire in modicella varies greatly in length, the short-spired 
individuals being the form commonly known as humilis. No line can 
he drawn between the short and long-spired specimens, as every kind 
of intermediate form occurs. (See the figures on plate XXIX.) From 
the records it would appear that Say at first considered the narrower 
form the same as his humilis, for he says in his description: “A va- 
riety of it, sometimes quite black, was found by Dr. McEwen, at 
Owego, on the Susquehanna.” Under modicella he writes: “It was 
found by Dr. McEwen at Owego, on the Susquehanna River, near 
the state of New York.” There is no question, I think, but that modi- 
cella was founded on the same specimens spoken of under humilis, 
and it also seems evident that Say considered them distinct from his 
North Carolina humilis. The types of modicella are preserved in the 
Philadelphia Academy and conform closely to Binney’s figure and to 
the shells figured on plates XXTX and XXXI of this monograph. 
Lea’s jamesii (pl. XXXI, fig. 1), of which the cotype is in the 
