NATURAL SCIENCES OE PHILADELPHIA, 
421 
straight hinge-line. Surface of cast nearly smooth; pallial line distinct, en¬ 
tire. Surface of shell showing only five irregular lines of growth, without 
undulations. 
Length over umbonal slope *64 (100); diameter at right angles with this 
dimension *50 (77); convexity of left valve *15 (23). 
Locality. —Marshall. 
Named in honor of C. A. White, M. D., of Burlington, Iowa. 
Posidonomta mesambonata, n. sp. — Shell small, tumid equimarginal. 
Beaks prominent, slightly incurved; umbonal slope passing scarcely anterior 
to the middle of the valve, and nearly at right angles with the short, straight 
hinge-line ; posterior margin slightly curved, scarcely alate, obtusely angula- 
ted at its junction with the dorsal side ; anterior margin similar to posterior, 
and connected with it by the semi-circular ventral margin. Entire surface 
convex, without undulations, and marked only by fine striae of growth. 
Length from beak to opposite ventral margin over umbo *50 (100) ; width 
at right angles with this line across the middle (and widest part) of the valve 
•41 (82); convexity of right valve *12 (24). ’ 
Localities. —Marshall and Moscow. 
Almost an exact copy in outline of P. vetusta, Sow. (de Kon. Anim. Foss., 
pi. vi. fig. 1, a and b, not c.) It wants, however, the undulations of that 
species, and is smaller. 
Sanguinolaria, McCoy. 
Sanguixolaria similis, n. sp.—Shell rather large, transversely elliptic, rather 
appressed. Beaks a little anterior to the middle of the shell, flat, obtuse, and 
little elevated. Hinge-line about one-third the length of the shell, slightly 
angulated under the beaks ; buccal and anal slopes somewhat straight; ante¬ 
rior and posterior margins abruptly rounded; ventral margin regularly curved, 
except a slight bend in the middle. Longest dimension equidistant between 
beaks and venter. Pallial impression entire ?; anterior muscular scar 
roundish-oval; posterior obliquely pyriform. A pair of strong internal 
ridges diverge from beneath the beaks (as in Tellina), the anterior passing 
along the posterior side of the buccal scar, and the posterior along the front 
margin of the posterior scar, terminating opposite the lower borders of the 
respective scars. A sharp but shallow groove runs along the anterior of the 
posterior ridge. Hinge not fully known; a strong triangular cardinal tooth 
passes a little obliquely forward across the hinge-plate, behind which is a 
deep pit, while a shallow one bounds the tooth anteriorly; an elongated tri¬ 
angular lateral tooth extends in front of the beak, and apparently another 
behind the beak. Shell thick; external surface marked by irregular, fine 
incremental striae, and a few broad shallow furrows. 
Length 2*0 (100); height 1*11 (55); convexity of one valve *23 (11); length 
of posterior lateral tooth ’42 (21) ; from beak to anterior extremity *95 (47) ; 
to posterior extremity 1*25 (62). 
Locality. —Marshall, where it is rather abundant. 
Sanguinolaria septentrionalis, n. sp.—Shell of moderate size, equivalve, 
quadrately elliptic, subtumid, with sub-central beaks. Hinge line occupying 
three-fourths the length of the shell, nearly straight. Posterior extremity 
roundly truncate by a plane inclining towards the beaks ; anterior end simi¬ 
larly truncated by a plane parallel with the last; ventral border slightly ar¬ 
cuated, bounded behind by a rounded acute angle, and before by a rounded 
obtuse angle. Hinge (as shown by casts) consisting of a prominent triangu¬ 
lar cardinal tooth, and a lateral one each side—the posterior very slender. 
Pallial line entire (?) ; anterior muscular scar small, nearly circular. Clavi¬ 
cular ridges indistinct. Surface of casts showing a few obscure incremental 
furrows. 
Length 1*15 (100) ; height *73 (63); convexity of left valvs *15 (13). 
1862.] 29 
