NATURAL SCIENCES OF PHILADELPHIA. 231 
in obliqua, ovalis, Totteniana (fig. 71), campestris, lineata, and 
effusa; there is a median projection to the cutting margin, some- 
_ times broken by the ends of ribs. These ribs are found in S. Tof- 
teniana (3) (see fig. 71); S. obliqua (3-7) ; ovalis (over 7); I de- 
tected no ribs on that of S. avara, lineata, campestris, Nuttalliana, 
| Sillimant, or effusa. 
Fig. 71. Fig. 72. 
Ce 
Jaw of Succinea Totteniana. Jaw of Succinea avara. 
[Morse.] 
The general arrangement of the lingual membrane is shown in 
fig. 73 of S. avara, while the characters of the separate teeth 
. Fig. 73. 
appr a : 
Lingual dentition of Succinea avara. 
are better seen in pl. XV., fig. 8. The peculiar character of the 
dentition is the cutting away or thinning of the middle portion of 
the lower edge of the base of attachment in the central teeth, 
and the inner lower lateral angle of the base of attachment in the 
laterals and still more in the marginals. The marginal teeth are 
also often peculiar in the denticulation of their reflected cusps. 
They have usually two small outer side cusps, the inner the smaller, 
each bearing cutting points proportioned to their size. The reflec- 
tion of the teeth is also small in proportion to the base of attach- 
ment. In other respects the dentition of the genus is very much 
like that of the Helicine. 
Succinea Silliman (pl. XVILI., fig. 12) has 24—1—24 teeth. 
Succinea ovalis has not been examined by me. Morse gives 
80 rows of 40—1—40 teeth. 
