NATURAL SCIENCES OF 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. 



Posidonomya 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. 



Sa-nguixolaria, McCoy. 



Sangpinolaria 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 farrows. 



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 valve -15 (13). 



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