1905.] NATURAL SCIENCES OF PHILADELPHIA. 269 
The penis is well developed, its lower part being muscular, and pli- 
cate within, the upper part thinner and densely, finely papillose inside. 
The epiphallus is well developed, withfterminal vas deferens or with a 
terminal tubercle (representing the flagellum) and a sublaterally in- 
serted vas deferens. The vaginais rather long. The globular or ovate 
spermatheca terminates a slender duct nearly as long as the uterus. 
Reproduction is viviparous. 
The retractor muscle of the penis arises from the apex of the penis 
and base of the epiphallus, or from the epiphallus near its base, and is 
inserted on the lung floor. The right ocular retractor passes between 
the co‘ and @ branches of the genitalia. 
The jaw is strong, arcuate, its anterior face more or less distinctly 
striated vertically; and there are sometimes very weak traces of ribs. 
The radula is of the ordinary Helicid type. Insome species the median 
area has unicuspid teeth, the cutting-edges usually overhanging the 
sides of the mesocone; while in others distinct ectocones are developed 
in all the teeth. The marginal teeth are bicuspid, the cusps unsplit 
as a rule, though there are exceptions where the inner of the two cusps 
is bifid. 
Type Helix strigosa Gld. Distribution, Rocky Mountain region from 
the Canadian to the Mexican boundary. 
This dominant type of Helicide in the area indicated above formerly 
extended farther east, one species occurring in the loess of lowa, and 
there is one outlying species westward, O. avalonensis Hemph., on 
Catalina Island, California. In its present area the type has been in- 
terminably modified into local races of all grades of differentiation, 
more than fifty of these having received names.® It is true that in some 
ranges every canyon—I might almost say every rock-heap—has its own 
race; but in a broader view it is seen that a single strain usually extends 
over an entire range with numerous minor modifications, and with 
inereasing elevation a general diminution of size, loss of sculpture and 
often intensification of color. These reduced forms are probably due 
to the diminished food supply and especially the shorter growing season 
in the heights—factors subject to great local variation, even at equal 
$6 The number of species of Oreoheliz is uncertain. About fifty forms of all 
degrees of differentiation have been described and named. My treatment of the 
group in former publications (Manual of Conchology, VIII, p. 115, IX, p. 50; 
Catalogue of the Land Shells of America, etc., pp. 31, 82 (1898), was unduly influ- 
enced by the views of Binney and Hemphill, both of whom advocated the inclusion 
of the entire series as varieties of P. strigosa. The characters of the shells, 
penes and teeth indicate, in my opinion, that the species are somewhat numer- 
ous; but their notorious variability cautions us to beware of multiplying them 
without ample materials. 
