THE NATURAL HISTORY SURVEY. 227 
surface with about thirteen heavy ribs, which denticulate both 
margins (Fig. 60, J). 
Radula formula: 585+8+4+43+,8, (13—1—13); the cen- 
tral tooth has a rather wide base of attachment, attenuated at 
the lower outer corners and excavated on the lower border; 
the reflection is tricuspid, of which the center cusp is long and 
narrow, reaching to the lower edge of the base of attachment; 
the side cusps are very short. Lateral teeth similar to central 
tooth, but bicuspid, the inner cusp long and the outer cusp 
very short; the fifth lateral is modified by the shortening of 
the outer cusp. The marginal teeth are low and wide and 
denticulated by from three to five teeth, of which the inner is 
the largest and bifid. The cutting points of the central and 
lateral teeth are very short (Fig. 60). There are over 75 rows 
of teeth. 
Genitalia: Unknown. . 
Distribution: United States and Canada, from Maine to 
Manitoba and south to Texas. 
Geological distribution: Pleistocene; Loess. Upper Eocene 
of Isle of Wight. 
Habitat: Found on the edge of woodlands under and 
about pieces of wood and various kinds of débris. 
Remarks; This is a most characteristic species, which 
cannot be mistaken for any other. The peculiar parietal ribs 
are different from any other species found in our region. The 
animal is very slow and deliberate in movement and the shell 
appears to be much too large for it. The latter is carried 
perfectly flat and the animal moves about in a wabbly manner, 
This species seems to be confined to the northern and western 
regions. It has been seen by Mr. Jensen to prey upon Euconulus 
fulvus. 
KEY TO SPECIES OF PUPID&.* 
A; Aperture without teeth or folds. ..i. 06... cece buena weeees marginata 
B. Aperture with teeth or folds. 
a. Aperture squarish or rounded. 
1. Teeth few or wanting; never more than two, placed 
on the parietal wall. sn. 0... cece ec ceue tare aneenene corticaria 
2. Teeth numerous (five to seven), parietal tooth bifid 
or bicuspidate; one or two basal teeth. 
Teeth small, long, narrow, sharp, five in number, ; 
never filling the aperture; onlyone basal tooth... .procera 
+tTeeth large, massive, almost or quite filling 
the aperture. 
*Excepting Strobilops. 
