1905.] NATURAL SCIENCES OF PHILADELPHIA. 271 
1. Penis long, the distal half strongly twisted, there being two dis- 
tinct kinks, resulting in convolutions variously disposed, and of course 
not always falling the same in the same species or variety. O. strigosa, 
from Pecos, and O. elrodi (Pl. XIX, figs. 3 and 2) belong here. 
2. Basal half of the penis swollen and muscular, the distal half 
smaller, without distinct kinks. O.s. huachucana and O. barbata (PI. 
XIX, figs. 6 and 5) are of this type. 
3. Penis small, short, the basal half not much larger than the distal 
portion, the latter not kinked. O. neomexicana and O. yavapai (PI. 
XIX, figs. 7 and 9) have penes of this kind. 
All the above have the penis longer than the epiphallus. In the 
subgenus Radiocentrum the epiphailus is as long as the penis or 
Jonger. 
As yet my observations have covered only about a dozen of the num- 
erous species and subspecies; and until more of the forms of the central 
and northern States are examined, characters of the soft anatomy 
cannot be fully utilized in classification. 
There are two types of dentition in Oreohelix. The ordinary forms 
have unicuspid central and inner lateral teeth. Here stand O. strigosa, 
cooperi, newcombiana, huachucana, yavapar, neomexicana and hayden. 
In the second type of teeth ectocones are developed on all of the teeth, 
the centrals being thus tricuspid, the lateral and marginal teeth all 
bicuspid. Of this kind are O. idahoensis, O. hemphilli, O. barbata, O. 
chiricahuana and O. clappi, but in the last species the ectocones are not 
well developed. 
The series of Huachuca Orcohelices shows that colonies of the same 
original stock vary greatly and often show parallel variations in differ- 
ent canyons. 
Those from the greatest altitudes are smallest (Pl. XXIV, figs. 25-27, 
29-32, Limestone Mountain, 8,000 feet; Pl. XXIV, fig. 28, Carr Can- 
yon, 7,000 feet, ete.), though some large shells occur elsewhere at equal 
elevations. 
Conspicuously banded shells were taken only at high elevations 
(Pl. XXIV, figs. 17, 18, Brown Canyon, 7,000 feet), plainer ones occur- 
ring lower down in the same canyon; but not all the high altitude 
shells are so marked. 
Gerontic or senile individuals or colonies are common, manifested 
by deep descent of the last whorl in front, with a tendency to form a 
free or solute peristome (Pl. XXV, figs. 33-35, Ida Canyon). 
The carinate periphery is an ancestral character of O. strigosa and 
its allies, present invariably in the neanic stage. It will be noted that 
