1905.] NATURAL SCIENCES OF PHILADELPHIA. 255 
Generic Characters of Sonorella. 
The genitalia (Pl. XX) show no accessory organs on the female side. 
The vagina is long; the spermatheca is globular or ovate on a very long 
slender branchless duct. The atrium is always extremely short. The 
penis is a well-developed, thin-walled tube, containing a large papilla, 
and terminating in a well-developed epiphallus. There is always a loose 
sheath or wide collar enveloping the base of the penis, and attached 
by muscular threads to the end of the epiphallus, which is thus held 
loosely in a reflexed position. This sheath has been removed in most 
of my figures, as it obscures the parts enveloped. 
The retractor muscle is attached to the epiphallus close to the penis, 
and is adnate to or envelops it to the apex of the latter. The fla- 
gellum is extremely short, or even absent. The details of structure 
are much varied in the several species as described below under each 
specific caption, and in the table of measurements. 
The free muscles, pallial complex and digestive tract have been de- 
scribed in these Proceedings for 1900, p. 558. No material differences 
have been observed in additional species examined. 
The jaw has four to eight ribs grouped in the median part, and either 
strong or weak, as in the Californian Helices (Pl. XXIII, figs. 18-23). 
The radula has unicuspid middle and lateral teeth, bicuspid transi- 
tional and inner marginal tecth and low, wide marginals with both 
cusps bifid. Exactly the same type of teeth occurs in the Californian 
Epiphragmophoras, in Ashmunella, Polygyra, etc. 
The upper surface of the foot is densely pebble-granose, with rather 
indistinct dorsal grooves; the genital furrow is undeveloped except 
near the mantle. The tail is depressed, rather long, and sometimes has 
a weak median impressed line along the top. 
In my original diagnosis of Sonorella I stated that the shell was 
“neither malleate nor spirally striate.” Mr. Bartsch has also asserted 
that “incised spiral lines are never present in this genus.”’ This state- 
ment must now be withdrawn, since several forms discovered by Mr. 
Ferriss show impressed spiral lines; but they are inconspicuous, and 
visible only under the lens.* To the eye, the shells of all known Sonorel- 
las appear nearly smooth, the sculpture, aside from slight growth- 
wrinkles, being microscopic. This is somewhat remarkable because 
they often live in the same rock-piles with rudely sculptured Oreohelices. 
