626 TRANS. OF THE ACAD. OF SCIENCE. 
radiate to the periphery, where they are strongly curved 
backwards. There are also obscure revolving lines on this 
part of the shell. The band of the sinus is rather deeply 
excavated, and bears closely set arched striz. 
Length, 9 lines; width, 11 lines. 
This beautiful shell resembles more closely P. variata of 
De Koninck than any other species known to me. The gene- 
ral form and proportions are similar, but the ornamentation 
is quite different. 
There is only one specimen of this shell in the Texas State 
Collection. It was found in the Coal Measures of Palo Pinto 
County, not far from the Brazos River. 
Dedicated to its discoverer, Dr. W. P. Riddell, of the 
Texas Geological Survey. 
PLEUROTOMARIA GLANDULA, NR. Sp. 
volutions about six, flat or very slightly convex, angulate 
the band of the sinus being situated between the second op 
third from the base. The volutions are also marked wit 
numerous sharp, flexuous, transverse aE which are inter- 
with 12-13 sharp, age ae lines, and Oech 
defined, and exhibits arched striw, much finer than those of 
the remainder of the volution. 
Length, 0.34; width, 0.36. 
Form. and Loc.—Coal Measures, Buchanan County. 
Texas State Collection. 
Murcuisonia TEXANA, 0. SP. 
‘Shell elongate conical, spiral angle 25° 5 volutions pi 
angulated ; suture distinct, linear; umbilicus none; @P® or 
rounded, subquadrate, its width and height pecs 7 ai 
last volution angulated at base and flattened convex Den™ 
