GASTROPODA. 969 
Lophospira serrulata.] 
edge is merely wavy instead of toothed, while on the last or free whorl of old 
specimens the prominences are, if not wanting entirely, at least much more irregu- 
larly developed. In all the body whorl has four nearly equidistant sharp carine, 
one on the upper slope a third or a little more of its width distant from the suture, 
a third beneath the peripheral one already described, and a fourth marking the 
limits of the rather large umbilicus. The latter has a distinctly convex slope, while 
the space between the third and fourth keels is gently convex in the middle, those 
between the peripheral one and the third and first decidedly concave, and that 
between the summit of the first keel and the suture line more gently hollowed out. 
As long as the whorls are in contact the upper edge is sharp so that the suture is 
not excavated, but soon after the last turn becomes free this edge is lost, the whole 
upper surface, that is, above the first carina, becoming almost uniformly rounded. 
Aperture, excepting the angulation at the peripheral carina, subcircular; in a side 
view the outer lipis deeply notched at the principal carina and somewhat angularly 
produced at the extremities ‘of the first and third keels. Surface marked with 
regular strong sharp equidistant lines of growth on the upper whorls, the striz 
becoming more irregular and assuming an aged appearance on the free last turn. 
Their number in a given space varies, but the average at the first or upper carina is 
about three in2mm. The direction of the strive, beginning at the suture, is first 
gently backward and then with a slight forward curve to the summit of the first 
carina. From here they sweep regularly and very decidedly backward to the 
peripheral keel, and beneath this forward again in a corresponding degree to the 
third carina on which they make a rectangular turn and proceed with less curvature 
than above to the fourth or umbilical keel. In the umbilicus, finally, the last 
backward direction continues until overcome by the curve when a transverse course 
is maintained until the circuit is completed on the upper side of the whorl. 
In casts of the interior of young individuals all save the first three whorls, 
which are but rarely preserved, may preserve in a decided degree the angularity 
which marks the exterior, but in fully grown examples only the last whorl retains 
the angles and even here the peripheral carina only is distinct. (This is one of the 
points relied upon in distinguishing internal casts of this and the next species.) 
We have very little doubt of the specific identity of this common shell of the 
Stones River group in Minnesota, Wisconsin and Illinois, with the Murchisonia 
serrulata described by Salter from the Black River group of Canada,* We grant 
that Salter neither mentions nor figures his species as having the last volution 
uncoiled, but this is readily explained if we assume, and his illustration justifies us 
in doing 50, that he had only young or imperfect examples. We have numerous 
* With the Canadian geologists this term includes the Birdseye or Stones River group. 
