PRODUOTELLJE OF THE CORNIFEROUS LIMESTONE. 
133 
“ gated bases. The distribution of these tubes has no regularity : they 
“ are cylindrical, rather short, and appear to have followed a direction 
“ parallel to the curvature of the' va<lve : they are more closely arranged 
“ towards the little ears than upon other parts of the surface, and, upon 
“ each side of the beak, form a range af four or five tubes directed back- 
“ wards, extending a little distance beyond the cardinal line. The ears 
“ are very small and fragile, and are terminated exteriorly in an obtuse 
“ angle. The cardinal line is shorter than the transverse diameter. On 
“ careful examination, we observe an extremely narrow area, divided in 
“ the middle by a triangular opening which is obliterated and hidden by 
“ the beak when the shell is placed upon its dorsal valve. Nevertheless 
“ the beak is very short and little prominent, although gibbous at a 
“ little distance from its extremity, and neatly separated from the 
“ ears by a sudden curve. The ventral valve is entirely embraced 
“ by the dorsal valve, in which it is deeply inserted, and which it fol- 
“ lows in all its contour : it is garnished with some concentric wrinkles, 
“ somewhat strongly defined upon the ears and upon the sides. Little 
“ rounded fossets are irregularly distributed, and correspond to the ori- 
“ gin of the tubes of the other valve.” 
“ Dimensions. Average length, 16 millimetres. Proportions of length, 
breadth, height and thickness=100 : 113 : 65 : 20. The total number of 
tubes varies from 25 to 50.” 
Prof. DeKoninck remarks that this species is known in America by the name 
of Strophomena lachrymosa. The Strophomena lachrymosa of Conrad was described 
from the Chemung-narrows in New-York, and is a larger shell, with different cha¬ 
racters from any one known to me in the Corniferous limestone of New-York or of 
the West, and does not at all resemble the figures of P. subaculeatus given by this 
author. 
Geological formations and localities . This species has been cited by M. DeVer- 
neuil as occurring at Charleston landing and Lewis creek in Indiana, and as tra¬ 
versing the Hamilton, Portage and Chemung groups. The specimen figured on 
Plate xxiii is from the Corniferous limestone at Jeffersonville, Indiana; and I pre¬ 
sume is identical with specimens from Charleston landing. 
I am unable to identify it with any species in the Hamilton and Chemung 
groups of New-York, though resembling some of those which I have placed under 
P. shumardiana. A larger collection of specimens may possibly show a passage 
from the one to the other. 
