GASTROPODA. 1017 
Hormotoma bellicincta.] 
Hormotoma BELLioinotTa Hall. . 
PLATE LXX, FIGS. 15-17. 
Murchisonia bellicincta HALL, 1847, Pal. New York, vol. i, p. 179,*pl. xXxX1Lx, figs. la and 1b, ? 1c and 
1d, not le. 
Hight 20 to 45 mm., apical angle 42° to 50°, generally about 44°; volutions neatly rounded, some- 
times appearing a little flattened in the upper half, rather closely wound, depressed so that the hight and 
width is respectively as one is to two, about six or seven in number, casts, however, rarely preserving 
more than four; band wide, flat, clearly defined on shells, just above or exactly in the middle of the 
whorls of the spire; lines of growth strongly recurved to the band, regular, comparatively strong and dis- 
tant, rarely visible on casts of the interior; a small, sometimes sharply defined umbilicus; aperture 
rounded, except at the lower angle, which is somewhat extended. 
At least two species were united under the name Murchisonia bellicincta by Hall and most subse- 
quent authors who have had occasion to write about the species, while collectors have used the name in a 
very loose and shifty manner. That Hall’s original figures (loc. cit.) embrace at least two species must be 
evident to all wh» will take the trouble to compare his la and le. How could the former, representing a 
small testiferous specimen, possibly be the apical portion of an example of the same species as the original 
of the latter, which is said to be an incomplete “cast of a large specimen”? In the first place, the apical 
angle of la is about 50°, while that of le is only about 32°. So great a difference, especially in a genus of 
shells in which the apical angle is unusually constant, almost certainly indicates specific variation. 
When we add that in corresponding parts of the two figures the one has four whorls where the other has 
but three, we may well wonder how the fact has so long escaped observation. Both forms occur in Min- 
nesota, and our only difficulty has been to decide as to which is the better entitled to retain the name 
bellicineta. 
So far as known, neither occurs in any disvision of the Cincinnati period, and both appear to be 
confined strictly to the Trenton proper. The larger form, however, seems to be the more common of the 
two and therefore probably the form that has been the more frequently referred to by authors. On the 
other hand, the smaller species precedes the larger on the plate, and, as the specimens figured of it are in 
a better state of preservation than the other, it is reasonable to assume that they furnished the greater 
part of the characters brought out in Hall’s description. We have therefore concluded to restrict the 
_application of the name bellicinctu to forms of the type of Hall’s figs. la and 1b, and propose a new desig- 
nation for the species represented by his fig. le. 
Formation and locality—Not uncommon in the Trenton limestone in New York and Canada. In 
Minnesota we have collected a total of eleven specimens, all from the lower part of the Fusispira bed at 
various points in Goodhue county. 
Collections.—E. O. Ulrich; W. H. Scofield. 
Hormotroma TRENTONENSIS, 7. Sp. 
PLATE LXX, FIGS. 13 and 14. 
Murchisonia bellicincta (part.) HALL, 1847, Pal. N. Y., vol. 1, pl. XX XIx, fig. le (not 1a-1d); OwxEN, 1852, 
Geol. Rep. Wis., lowa and Minn., pl. u, fig. 8. 
Murchisonia major WHITFIELD, 1882, Geol. Wis., vol. iv, p. 244, pl. 1x, fig. 4 (not MZ. major Hatt). 
Hight 30 to 100 mm., apical angle 32° to 37°, generally about 35°; volutions seven or eight, almost 
uniformly convex from suture to suture, not very closely wound, with the hight and width respectively as 
2is to 30r3to5; band median, wide, flat, the lunule very moderately curved; lines of growth regular, 
fine, somewhat thread-like, averaging about eight in 5 mm., with the usual backward curve; notch deep 
and wide; mouth greatly produced and turned backward below; inner lip thin, reflected, above partly 
covering a small umbilical perforation. 
This beautiful shell has been for many years confused with H. bellicincta Hall sp. On the preceding 
page we give our reasons for restricting Murchisonia bellicincta to the smaller of the two species figured by 
