GASTROPODA. 997 
Liospira angustata.] 
resemble that species very closely (for comparisons see preceding page) the affinities of L. progne are really 
much nearer L. micula Hall sp. Indeed, the last is probably nothing more than a dwarfed variety of 
L. progne, and if it were not for the fact that it held its own with remarkable constancy through a 
long period and is perhaps the most common type of the genus, we would be inclined to place its name 
on the list of synonyms. The closed umbilicus distinguishes both very easily from L. americana, L. 
vitruvia, and other species of the genus having an open umbilicus, while the extreme faintness of their 
suture lines and the flatness or slight convexity of the upper surface of their volutions separates them 
at once from such close allies of L. helena Billings sp. and L. persimilis Ulrich. 
Formation and locality.—Stones River group, Murfreesboro and Lebanon, Tennessee; Black River 
and Trenton groups, Mercer county, Kentucky, and near Ottawa, Canada; Trenton group, Clitambonites 
and Fusispira beds, Goodhue and Fillmore counties, Minnesota. 
Collection.—E. O. Ulrich. 
LIOSPIRA ANGUSTATA, 7%. Sp. 
PLATE LXVIII, FIGS, 85—37; PLATE LXIX, FIGS. 1—2. 
Stones River group variety: Width about 17 or 18 mm., hight about 9 mm.; apical angle 125°. 
Trenton group variety: Width 29 to 45 mm., hight 15 to 22 mm.; apical angle about 130°. Number of 
volutions four to five. 
This species, casts of which are exceedingly like those of L. americana and L. progne, is distinguished 
from the former by the great and gradually increasing deposit of shell-matter on the umbilical side of the 
whorls, and from the latter by the fact that this deposit does not, as is the case in that species, fill the 
umbilical cavity entirely, but leaves a narrow subcentral perforation. As shown in figure 37 on plate 
LXVIII, the umbilical perforation is relatively much larger in the younger stages of the shell than it is 
in fully grown examples, showing that the deposit, which we take to be a callous reflection of the inner lip, 
was proportionally much greater in later stages of growth. The callosity did not spread itself over the 
bottom of the umbilicus but was confined to its sides, and herein lies the principal difference between 
L. angustata and L. progne. Another difference is that the anterior outline of the lower lip is more broadly 
and less uniformly convex. 
Formation and locality.—Of the small Stones River group variety we have four specimens which 
one of us collected in the Vanuxemia bed at Minneapolis. Of the larger variety, which occurs in the 
Fusispira bed of the Trenton group at several localities in Fillmore county, we have five specimens. 
Collections—Geological and Naturai History Survey of Minnesota; HE. O. Ulrich. 
Museum Register, No. 7494. 
LIOSPIRA OBTUSA, ”. Sp. 
PLATE LXVIII, FIGS. 30—34. 
Hight of a large specimen 25 mm., width of same 44 mm.; hight of asmall example 17 mm., width of 
same 32mm. Volutions four to five, with the periphery rounded and the upper side very slightly convex. 
Umbilical cavity rather large in casts but in the shell itself it is filled, excepting a minute central 
perforation, by a distinctly outlined, thick external deposit on the inner side of the whorls. This deposit 
is as heavy relatively on the inner whorls as on the last. The last feature, together with the obtuse 
character of the periphery, distinguishes this species from L. angustata. 
Among a lot of Lower Silurian Gastropoda kindly sent us by Prof. J. M. Safford, we find two speci- 
mens which he collected from the ‘‘ Ridley limestone” in Rutherford county, Tennessee, which agree in 
all respects with this species save that the umbilicus is not constricted by a deposit of shell such as we 
find in this and the preceding species. The umbilicus is about as large as in L. vitruvia but the margin of 
it, though rather abruptly rounded, is not angular as in that-species. We believe these specimens 
Tepresent another undescribed species of this important genus and one that, if time and space had 
