1909.] NATURAL SCIENCES OF PHILADELPHIA. 499 
In one specimen dissected it bears a minute diverticulum about 1 mm, 
long, 2 mm. from the base of the duct. In another individual no 
diverticulum was found, so that it may possibly be abnormal or 
pathologic. The measurements of the organs in two individuals 
preserved in formalin follow: 
No. 94,384. No. 94,358. 
Length of DENIS) 00°).. Westie: Pie fide Pix’ SiO LATTA: 41 mm. 
Penis aApulate wae re eee Ba 
Deeye qemipnaiiis,. ety Les AQ 60°" 
ire enacellomi re Ps ey ae Sea 
VPI, eee ages PLDs Bo a 
72) ans spermatheca and duct, VOU epee ari tS PR os 
The jaw (pl. XXII, fig. 6) has five strong ribs grouped in the middle 
half of its length. 
The radula has about 41, 1, 41 teeth (pl. XXII, fig. 8). The central 
and lateral teeth have mesocones only ; on the 17th an ectocone appears. 
On the outer marginal teeth the inner cusp or sometimes both cusps are 
bifid, but the ectocone is not split into several cusps as in some other 
species. 
The excessive length of penis and epiphallus, and especially the 
hollow, thin-walled papilla containing a separate duct or tube (a 
structure unique in the genus), are characters which set S. dalli apart 
from all other known Sonorellas. It stands alone in its own line of 
differentiation. 
Group of S. granulatissima. 
- These forms are closely related to the group of S. hachitana, but 
differ by the thick, quite cylindric penis-papilla, solid except for the 
minute perforation, and very obtuse or truncate at its distal end, 
and by having no flagellum or only a minute vestigeal one. In the 
hachitana group the papilla tapers, at least at the distal end, and a 
minute but distinctly developed flagellum is present in known forms. 
The distinction is only a small matter, but serves to distinguish the 
Huachucan forms. 8S. rowelli (Newc.), from a little farther west, 
belongs to the same group. 
The dimensions of the genitalia in several specimens of each form 
are given in the accompanying table. Most of the specimens were 
preserved in alcohol in the field, and some variation is doubtless 
traceable to various degrees of contraction. 
