GASTROPODA. 829 
Archinacella powersi.] 
this type described in the following pages, we refer to Metoptoma instabilis Billings 
(Quebec group), JM. simplex Billings (Calciferous group), MM. trentonensis Billings 
(Trenton group) and M. estella Billings (Hudson River group). 
In addition to the species of which descriptions follow and those mentioned in 
the preceding paragraph, we regard Tryblidium piliolum Whitfield, T. canadense 
Whiteaves, Metoptoma phillipsi Walcott, and M. similis Whitfield, as belonging to 
this genus. 
ARCHINACELLA POWERSI, #. Sp. 
PLATE LXI, FIGS. 3—5. 
Shell large for the genus, moderately convex, subovate, widest in the anterior 
half; anterior outline semicircular, the posterior semielliptical; margins of aperture 
rather strongly arcuate; apex rather blunt, slightly incurved, the extreme point 
just over the margin and at least two-thirds of the greatest hight of the shell above 
it. Surface with fine, distant, impressed lines of growth; near the margin the 
markings become somewhat lamellose. Length 29 mm.; width 25 mm.; greatest 
hight 10 mm.; hight of apex 6.5 mm. 
_ Impressions of the interior markings are excellently preserved on the cast 
figured on plate LXI. The loop of muscular scars forms one continuous narrow band 
curving distinctly down in front so as to pass beneath the apex. The posterior 
third is somewhat wider and prolonged on the outer side into numerous irregular 
processes. Within the anterior end of the loop we see the pair of rostral scars, and 
just behind them a narrow pair lies close to the band. Finally, we observe faint 
impressions of a larger anterior pair without the band, which may be called antero- 
laterals. 
This fine species is readily distinguished from all described heretofore. Collec- 
tors seem to have confounded it with A. perovalis Whitfield sp., which occurs in the 
same strata, but is smaller, decidedly narrower—in front especially—and has the 
apex not quite marginal. 
Formation and locality.—Stone’s River group, Beloit, Wisconsin, where the types-were collected by 
Mr. H. C. Powers, for whom the species is named. 
Collections.—University of Wisconsin; E. O. Ulrich. 
ARCHINACELLA CINGULATA, ”. sp. (Ulrich.) 
PLATE LXI, FIGS. 1 and 2. 
Shell large, rather strongly convex, subovate in outline, very broadly rounded 
in front, more narrowly behind; hight, width and length respectively as 4.5 to 10 to 
12; margin of aperture horizontal; apex bluntly pointed, curved downward to about 
