NATURAL SCIENCES OE PHILADELPHIA. 
413 
This species differs from P. elongata, Goldf. (Petref. Germ. ii. 135, Taf. cxix. 
5), in having a much smaller body, and less distinct from the alate extrem¬ 
ities. 
Mytilus, Linnaeus, 
Mytilus Whitfieldianus, n. sp.—Shell small, ventricose, transversely elon¬ 
gate, very oblique, with terminal beaks. Hinge line two-thirds the length of 
the shell, forming a rounded, very obtuse angle with the somewhat circular 
posterior border ; ventral border slightly arcuate, more rapidly curved beneath 
the beaks. Greatest width opposite the posterior extremity of the hinge-line. 
UmbQnal ridge elevated, crowded over towards the hinge line, and rendered 
somewhat angular, more sharply so towards the beak. Surface of shell and 
cast marked by numerous concentric lamellose lines. One of the best preserved 
specimens shows distinctly a multitude of minute diverging strise running in 
all parts of the surface at right angles with the lines of growth. 
Length from beak to posterior extremity *59 (100) ; greatest height *29 (50) ; 
length from beak to extremity of hinge line *44 (75) ; convexity of right 
valve *12 (20). 
Localities. —Holland, Ottawa county and Marshall. 
Cardinia, Agassiz. 
Cardinia complanata, n. sp.—Shell of moderate size, ovoid, compressed, 
with sub-central beaks. Ventral border gradually curved to the abruptly 
turned extremities, from which the outline is nearly straight along the cardi¬ 
nal slopes to the obtuse incurved beaks ; line joining extremities equidistant 
from beaks and ventral margins. Right valve flattened, producing an angular 
fold along the postero-dorsal declivity near the hinge line. Exterior sculp¬ 
tured by about 20 broad regular furrows parallel with the ventral border. 
Other characters unknown. 
Length 1*2 (100); height *64 (53) ; length of anterior cardinal slope to ex¬ 
tremity of shell *64 (53); of posterior '87 (72) ; convexity of right valve 
(perhaps mechanically compressed) '13 (11). 
Locality. —Union, in Branch county, in blue argillaceous shales of the Hu¬ 
ron group. 
Cardinia ^quimarginalis, n. sp.—Shell of medium size, tumid, beaks cen¬ 
tral, anterior and posterior hinge-slopes at right angles with each other, 
straight, very nearly equal and symmetrical; extremities rounded, situated 
about midway between beaks and ventral margin, which is regularly arcuate 
between the extremities ; posterior extremity a little more acute than the an¬ 
terior. Shell tumid, regularly convex, slightly truncate along the antero-car- 
dinal slope. Beak (of cast) marked only by obscure incremental lines and 
nearly obsolete concentric furrows. Hinge structure unknown. 
Length of shell -91 (100) ; height -86 (94); thickness -50 (55.) 
Locality. —Marshall. 
Cardinia robusta, J. de C. Sowerby is a close representative of this species, 
but is not so high, and is more produced and angulated posteriorly. 
a i vtirv * l 
Cardinia concentrica, n. sp.—Shell of medium size, ventricose, transverse¬ 
ly elliptic, with subequal extremities and marked ventra l enrolment. Beaks 
appressed, incurved, rising little above the hinge, distant one-fourth the shell- 
length from the anterior end ; umbo and middle of the shell flattened antero- 
posteriorly ; antumbonal ridge inflected towards the hinge, forming above a 
lunuliform area ; dorsal and ventral borders sub-parallel in the adult shell; 
posterior end obtusely, or at length truncately rounded ; anterior end para¬ 
boloid. Hinge line straight and rather extended posteriorly. A broad shal¬ 
low inconspicuous sinus extends from the posterior ventral margin towards 
the beak. External surface marked, towards the beak, with remote, equidis¬ 
tant, raised, concentric strise and intervening flat belts ; towards the margin 
1862 .] 
"SAUWi / 
