328 PROCEEDINGS OF THE ACADEMY OF [May, 
At Station 5 two broken examples, 
much weathered, were dug out of the 
soil. Though practically adult, the 
largest measures only 18.2 mm. diam- 
eter, the shell being quite as solid as 
in large individuals. It was probably 
dwarfed by the arid conditions be- 
fore it became extinct in this place. 
The genitalia are remarkable for 
the small size of the male organs. 
The penis is very slender, diameter 
1 mm., tapering downward, and en- 
circled at the base by a short sheath. 
The penis-papilla is very slender, 
gradually tapering, and annulate. The 
retractor muscle is terminal, long and 
Gi & slender. Epiphallus a little shorter 
Fig. 2.—Genitalia of S.hachi- than the penis. The vagina is slightly 
tana, with detail of penis- 1 fhanth : Ouhenas 
papilla. onger than the penis. er organs 
as usual. Measurements of the organs 
of two individuals are given in the following table, with those of 
allied forms for comparison. 
| | a 3 - 
| = E = aa 3 ‘ 
| Etch, eee ee eet oe 
| “2 a = = Sy Og | ak | = 
Ld fee eae Bel Be BES oem a ae 
S. hachitana.......cc...0ch 6.25) 4 | 4.2] 1.25] 7.5 | 19  |.......| 108,098 
ag OL eas tee: Sal oad gs AN Id eet LI tee a7 gy Ans Mee Ole oe 2 103,098 
Ste lords ac eae: 10 4.3) 6:2 1.110. | 03:94 Sears 94,329 
- eee ore 5.5 | 5 i Be 9 Tl eer ge Seeticee Seal es | 94,329 
& on) 4 625 sO Sb at HOS ae ei Ome leaner | 86,4 
S. h. peloncillensis........ ED ch 26 6224) oa Os seed 9.5 | 94,513 
10 / Ors2| ant L 20) Oy tl See | eee ; 
The well-arched jaw has 7 or 8 ribs. The radula has about 22, 16, 
1, 16, 22 teeth, both cusps becoming split on the marginal teeth. 
In my former work on S. hachitana (1905) I referred shells from the 
Organ and Florida Mountains and from central Arizona to S. hachi- 
tana, which at that time was not known anatomically. While it 
must be admitted that the shells are very similar, I find differential 
