208 TRANS. OF THE ACAD. OF SCIENCE. 
which, ne Mahon never attains ~ extraordinary thickness of 
the Americ n shell, nor do we find in our specimens the “ir- 
regular in sephisis da tun ailetion of the concentric wrinkles 
in front of “the middle” mentioned by McCoy (British Palxo- 
z0ic Fossils in Mus. Univ. Camb., p. 508). 
mensions.—A very gibbous va riety gives the _- 
proportions : Length, 2.08; height, 1.33; thickness, 1.21 
olga variety gives: Length, 1.84; height, 1.04; thick- 
8 
Geol. Pos. and Loc.—This fine speeies is from the Upper 
Coal Measures of the valley of Ve rider River, K. T. 
Collected by Maj. F. Hawn. 
Lerropomus ToreKaEnsis, Shumard. 
‘Shell ovate, sub-quadrate, length less than double the esr 
anterior margin descending obliquely from the beaks, stro 
pipe below ; anal margin oblique, subtruncate; palleal mar: 
gently arcu: arcuate ; seetipnl edge straight, bordered with 3 a 
slightly prominent carina; umbones moderately gibbous, ¢ 
tusely subangulated posteriorly, strongly rounded in front, 
most gibbous a short distance below the beaks, a slight de- 
pression rage qo toe ar be from beak to base; 
erior 
nent portion of. the v valves by but shallow li 
smus 5 puis or sack hee’ considerably pro ete above the 
‘the font po m. arked with serous mts concentric 
and become obsolete on the anterior slope, posteriorly they 
iniaun te at the inner eid : 
the umboni 
This sh 
, which are gently waved at the slight anterior depression 4 
