PERMO-CARBONIFEROUS PELEOYPODA — ETHERIDGE. 
185 
In Plenrophorus , as describod by King, and redescribed by 
Waagen,* the equivalve closed shell possesses two cardinal inter- 
locking teeth in each valve, and a posterior lateral one, extending 
the entire length of the hinge ; there is a lunule and an escutcheon, 
entire pallial lines, and fairly well marked adductor impressions, 
the anteriors having before them strong shelly ridges. 
Waagen has pointed out that “ one of (lie two cardinal teeth 
is often very little developed,” and such is the case in most of our 
specimens, but in a cast in the Geological Survey Collection, the 
impressions of all four teeth are distinctly visible. 
Pleukophoeus gregarius, sp. nov . 
(PI. xxxiii., figs. 2 - 5.) 
tip. Char. — Shell transversely elongated, oblong, robust, praeti 
cally maintaining the same width throughout its whole length, the 
latter on an average one and three quarter inches, depth one inch: 
dorsal and ventral margins straight, parallel ; bodies of the valves 
convex, most so at about the middle, but ( lie Hanks rather flattened 
or straight walled: faint cinctures exist, cutting the ventral 
margins at about the centre ; anterior ends small, the margins 
convexly rounded ; posterior ends but slightly flattened, the 
margins rounded ; umbones conspicuous and incurved, a little 
flattened above; escutcheon long, widening posteriorly; lunule 
apparently cordiform, shallow ; posterior cardinal teeth below the 
umbones, the most anterior of the left valve often inconspicuous ; 
posterior lateral teeth leaving deep impressions in casts, the left 
often double; anterior adductor impressions deep, low in position, 
forming strong prominences in the cast, guarded by a posterior 
shelly ridge, which varies in intensity in individuals ; posterior 
adductor impressions faintly marked, continuous ; exterio-pallial 
margins flattened, leaving very conspicuous impressions in casts ; 
sculpture of concentric lamime, no radii. 
Obi s*. — With one exception this is only known to mo as casts, 
and in the adult state 1 find the measurements very constant. 
The exception referred to, otherwise possessing all the characters 
of the species, is two and three quarter inches long by one and a 
half deep. 1 have only seen one individual that may be P. yrayarius 
with the test preserved, but it is from a different horizon. The 
sculpture is concentric, with well marked lamime, but without 
any traces of radiating costae. P. greyarius belongs to the group 
Tmbricati in the classification of Waagen ;f and in outward form 
resembles to some extent all three species placed by him therein, 
but is a broader and moro robust form. 
*■ Waagen— Mem. Geol. Surv. India, Pal. Ind. (13), iii., 1881 (Salt 
Range Fossils, Pelechypoda) p. 214. 
f Waagen, loc. cit p. 210. 
