CLASS GASTROPODA 
89 
which lends to this part of the turn a finely blistered appearance. Post- 
nuclear whorls a little more than two, well-rounded, separated by a 
strongly constricted suture, marked by three, strong, rounded, spiral keels, 
of which the strongest is a little anterior to the posterior third between the 
sutures, while the anterior of the other two, which are of equal strength, 
is at the periphery and the third halfway between them. In addition to 
these keels, the whorls are marked by fine, incised, spiral lines between 
the keels, which are best developed on the well-rounded shoulder, between 
the summit of the whorls and the strong keel below it. Base of the last 
whorl slightly protracted, well-rounded, marked by two broad, depressed, 
spiral cords, of which the basal one, which is a little anterior to the middle, 
is the broader. In addition to these there are numerous, exceedingly fine, 
spiral striations. The axial sculpture of the entire spire and base consists 
of very fine, incremental lines only. Aperture very broadly ovate, almost 
circular; peritreme continuous; outer lip thick within, beveled at the 
margin to form a sharp edge, which is rendered slightly sinuous by the 
external spiral sculpture; inner lip strong and strongly curved; parietal 
wall of the aperture appressed to the preceding whorl. Length, 1.4; 
diameter, 1.2 mm. (Bartsch.) 
Type in United States National Museum, No. 208445. Type locality, 
Port Graham, Alaska. 
Range. Port Graham, Cook’s Inlet, Alaska. 
Alvania trachisma Bartsch, 1911 
Plate 80, fig. 7 
Proceedings of the United States National Museum, 41:339; PI. 29, fig. 7. 
Shell elongate-ovate, yellowish white. (Nuclear whorls decollated.) 
Post-nuclear whorls slightly rounded, marked by slender, well-rounded, 
almost vertical, axial ribs, of which 26 occur upon the first and second 
and 22 upon the third and the penultimate turn. These axial ribs are 
about one-third as wide as the spaces that separate them and extend promi¬ 
nently from the summit of the whorls, where they terminate in rounded 
cusps, to the umbilical area. In addition to the axial sculpture, the whorls 
are marked by spiral cords, of which 3 occur between the sutures on the 
first and second whorls, 5 on the third, and 6 on the penultimate turn. 
The spiral cords pass over the axial ribs as cords. The spaces inclosed 
between the axial ribs and the spiral cords are elongate oval pits, having 
their long axes parallel with the spiral sculpture. Suture broad and very 
deeply channeled. Periphery of the last whorl marked by a sulcus a little 
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