156 Trans. Acad. Sci. of St. Louis. 
species, figured by Prof. Harris on the same plate as the 
young of P. servatoidea Ald., with which it evidently has no 
relationship. This latter species seems in fact to be ex- 
ceedingly close to georgei, and appears to be from the same 
horizon. Mécrosurcula will include, in addition, the Upper 
Claiborne Fusus vetustus, of Lea, and two species from the 
Vicksburg Oligocene, one of which I recently described under 
the name P. intacta. 
Lyrosureula n. gen. 
The species of this genus bear some resemblance to those 
of Pleurofusia, but the spire whorls and ribbing are more 
cylindrical and the spiral lyrae are different in character, 
being equal and equally spaced among themselves below the 
fasciolar surface and not enlarged on the ribs to any very 
noticeable degree. They differ also in the embryo, which, 
although conical and multispiral, has the lower whorl or two 
covered with longitudinal riblets, these being absent in Plewro- 
fusia. The three species at present before me may be 
recognized by the following characters: — 
Embryo acutely conical, higher than wide, of 6 whorls, the apical or nucleus 
more swollen and slightly eccentric, the first three smooth, the lower 
three covered with very regular riblets which at first are very fine, 
close- set and feeble, becoming gradually coarser and more widely spaced, 
the sixth whorl gradually acquiring the spiral lyrae, these appearing 
distinctly between the riblets; fasciolar surface beginning abruptly at 
the end of the sixth whorl; next two whorls— the first two body 
whorls — having strongly rounded outline, about eleven feebly elevated 
and transversely rounded subcylindric ribs, three strong but narrow, 
well separated spiral lines in rather more than basal half and a decliv- 
ous, broadly concave fasciolar surface, with distinct arcuate lines of 
growth and twofine spiral threads and not entirely crossed by the 
rapidly obsolete ribs; subsutural collar very smalland feebly carinulate; 
canal short, slender and twisted. Length of a specimen having a com- 
plete exbryo and 2 body whorls, 4.3 mm.; width, 1.6 mm. Lower 
Claiborne Eocene of St. Maurice, La...............+.-- elegans 0. sp. 
Embryo less acute at tip, alittle higher than wide, of four whorls, the upper 
three smooth, the fourth alone with a few widely separated, obliquely 
arcuate and rather feeble riblets, body whorls nearly as in the preced- 
ing, with ten broadly rounded ribs distinct in the inflated subcylindric 
lower half of the whorls and scarcely intruding at all upon the steeply 
descending and broadly concave fasciolar surface; the sculpture 
