Casey — Notes on the Plewrotomidae. 147 
and covered with rather close-set, fine but sharply elevated threads, the 
one nearest the peripheral carina much the largest; surface below the 
peripheral carina cylindric, with a similar carina a little below its mid- 
dle and another near the lower edge; space between the peripheral 
carina and the one next below with a finer carina a little below its mid- 
dle. Length of afragment consisting of the embryo and 4 spire whorls, 
5.6 mm.; width, 3 mm. Lower Claiborne Eocene of St. Maurice, 
Tidipia'w alain nia Gu aiaiateltateletaeisiat'e clare anion ial ale! ole's\e/sisix'e's-e' ees «se MOMGOLOR Tl. SD; 
Mr. Aldrich mentions no crenulation on the periphery of 
the nepionic whorls of éwomeyi, but these are said to exist 
by Prof. Harris. 
Bathytoma Harr. et Burr. 
Dolichotoma Beli. (nom. praeocc.). 
According to Cossmann, this genus exists fossilized in all 
the Tertiary strata and is also found living, but I am inclined 
to believe that that author hasconfusedanumber of generic 
or subgeneric types and that the really typical Bathytoma 
occurs only in the upper European Tertiaries, where it is 
represented by Murex cataphractus Broc. The geologically 
much older American species, from the upper Eocene of Red 
Bluff and the Vicksburg Oligocene, described by Conrad under 
the name Pleurotoma congesta, is a much smaller species and 
differs in some respects, perhaps subgenerically, but may be 
considered a Bathytoma for the present. The peripheral ridge 
is much better marked than in Megasurcula and is frequently 
costulose and the obtuse oblique columellar ridge, very feeble 
in Megasurcula is conspicuous in at least the American Bathy- 
toma congesta. This ridge is not homologous with the colu- 
mellar plicae of some other genera, which are doubtless to be 
closely associated in any natural arrangement, such as Sco- 
binella, and, occurring much lower down on the columella, is 
probably different in origin and significance. 
Megasurcula nN. gen. 
The embryo in this genus is apparently paucispiral, but con- 
oidal, the canal obsolete, the base of the shell broadly obtuse, 
the pillar with an oblique ridge externally; sinus large and 
