1910.] NATURAL SCIENCES OF PHILADELPHIA. 95 
elevations than the Rucker Box (about 7,000 feet), so that the degen- 
eration is probably due to other local causes. 
SS 
Ss 
SSS 
Xi 
SA 
SS 
LTA 
Fig. 15.—0. b. minima P. and F., Rucker Canyon, Station 114a. 
Genus ASHMUNELLA Pils. and Ckll. 
A study of the genitalia of Chiricahuan Ashmunellas leads to the 
conclusion that all the species of that range are of common ancestry, 
and more closely related inter se than any are to New Mexican or 
Huachucan species. In other words, the specific differentiation has 
been mainly subsequent to the isolation of this fauna. 
In both Chiricahuan and Huachucan species the penis is bipartite, 
consisting of an upper and a lower portion separated by a submedian 
constriction. In the Huachucan 
series the wpper segment is enlarged 
like the lower (see plate XX, Proc. 
A. N. S. Phila. 1909). In 
Chiricahuan forms the upper seg- 
ment of the penis is very narrow, 
hardly larger than the epiphallus, 
but its distal end is invariably a 
little swollen, and _ contracts 
abruptly where it passes into the ee 
; ‘ aes Ca ig. 16.—Terminal ducts of genitalia 
epiphallus”’. The penis retractor of Ashmunella p.albicauda, Station 4, 
is extremely short in Chiricahuan White Tail Canyon. Sp, base of 
spermathecal duct; Ovi, base of ovi- 
species, longer in Huachucan. duct; P, lower, swollen portion of 
The spermatheca is more or less _ penis, Pp. Upper end of penis. 
varicose in Huachucan species, 
but this is hardly apparent in Chiricahuan forms. The vagina in the 
Chiricahuan series is swollen and muscular in its upper part, smaller 
with thinner walls below. In other respects the organs are alike in 
the two series. These considerations lead to the conclusion that the 
whole Chiricahuan series of Ashmunella constitutes one phylum, the 
Huachucan series another. Doubtless the two phyla were of common 
ancestry; but their evolution on the two parallel mountain ranges 
has been independent. The extraordinary resemblances between 
some Chiricahuan and Huachucan species, which led us in 1905 to 
2 The slender upper continuation of the penis was not always recognized in 
our former (1905) work on Chiricahuan snails, although once understood it is 
clear enough. 
