284 RESEARCH IN CHINA. 
curve. Pedicle valve strongly elevated at the beak, the surface sloping from the 
umbo to the anterior and antero-lateral margins with a slightly convex curve, some- 
times becoming a little concave as it approaches the anterior margin, the slope to the 
cardinal extremities somewhat more abrupt; cardinal area large, flat, sloping pos- 
teriorly from the hinge-line in one specimen at an angle of 102° and in another at an 
angle of 115° to the plane of the valve, the cardinal margins sharp; delthyrium rather 
narrow, closed with a strongly convex deltidium, foramen terminal, encroaching 
upon the umbo; median septum inconspicuous; muscular impressions indefinite, 
rather large, and flabelliform. Surface of each valve marked by fine radiating coste, 
two or three of which occupy the space of 1 mm. 
The dimensions of two pedicle valves are: length 15 mm. and 14 mm., width 
18.7 mm. and 16.9 mm., height of cardinal area 5 mm. and 5 mm., greatest width of 
deltidium 3 mm.and 2.5mm. ‘The dimensions of a brachial valve are: length 16.5 
mm., width 21 mm., convexity 4 mm. 
This species is represented in the collection by only a small number of speci- 
mens, none of which are as well preserved as might be desired. It differs especially 
from other members of the genus in the terminal position of the pedicle opening, the 
pedicle apparently having passed through the foramen in a direction continuous 
with the surface of the deltidium and not at an angle to it, as is usually the case. 
This position of the pedicle also seems to have modified the position of the spon- 
dylium, its surface being nearly vertical to the inner surface of the valve, in con- 
sequence of which the median septum becomes essentially obsolete. 
Hemipronites tenuistriata Weller (plate 25, figs 21-24). 
1907. Hemipronites tenutstriata Weller, Proc. U. S. Nat. Mus., vol. xxxt1, p. 559. 
Shell wider than long, the valves subequally convex, the hinge-line a little 
shorter than the greatest width, the cardinal extremities subangular. Pedicle valve 
most prominent on the umbo, the beak rather obtuse, the surface sloping from the 
umbo laterally and anteriorly with a gently convex curve; a slight, scarcely noticeable 
mesial flattening of the valve occurs toward the front, but no mesial sinus is present; 
cardinal area flat, rather large, with a broad deltidium, the cardinal margins angular. 
Brachial valve most prominent along the median line, but with no differentiated 
median fold, the greatest convexity at about the mid-length of the valve, the surface 
slightly compressed toward the cardinal extremities. Surface of each valve marked 
by exceedingly fine strize which are scarcely visible to the naked eye, about eight 
occupying the space of 1 mm. 
The dimensions of a pedicle valve are: length 16 mm., width approximately 17.5 
mim., convexity 5 mm., height of cardinal area 3 mm., length of hinge-line 15 mm. 
The dimensions of a brachial valve are: length 17 mm., width 22 mm., convexity 5 mm. 
The specimens of this species in the collection are all too poorly preserved to 
allow the determination of its generic position with entire satisfaction. They have, 
however, the general form of European members of the genus Hemipronites and it 
is believed that this generic reference is correct, but the nature of the deltidium and 
the presence or absence of a foramen can not be certainly determined. The genus 
Hemipronites has not been recognized in the American faunas, and is known espe- 
cially from the Baltic provinces in Russia. ‘The species is evidently congeneric 
with the shell which Marielli has called Orthisina giraldii,' and the two species are 
closely allied. The species here described, however, is somewhat more finely striate, 
and it seems to be relatively a somewhat broader shell. 


‘Boll. della Soc. Geol. Ital., vol. xx (1901), p. 305. 
