582 



NEW SPECIES OF CRETACEOUS FOSSILS. 



CONCHIFERA. 



INOCERAMUS SAGENSIS. (N. S.) 

 (Tab. VII., fig. 3.) 



Specific character. — Subovatc or ovato-rhomboidal, convex, a wing-like exteusion of the anterior margin. 

 Beaks blunt, slightly prominent. Angle formed by the hinge-line and axis a little less than a right 

 angle. Broad, concentric, festoon-like, oval wrinkles of the surface. Length four inches ; width three 

 inches. 



Relations and differences. — This fossil approaches in form to /. mjjtcloides of Gold/., but it is wider 

 transversely, has no distinct concentric stria3 between the broad wrinkles; beaks blunter; more elliptical 

 in outline ; hinge-line longer. From I. Cripsii, which it also somewhat resembles, it difFers in being 

 much more gibbous, and in the direction and dimensions of the hinge. 



From the cretaceous formation on Sage Creek, southern tributary of the Cheyenne, associated with 

 /. Barabini (?) and I. Nebrascensis. 



INOCERAMUS NEBRACENSIS. (N. S.) 

 (Tab. VIII., fig. 1.) 



Specific character. — Obliquely subovate or flatly rhomboidal egg-shaped; moderately convex. Umbos 

 blunt and somewhat prominent. The hinge-line and axis form an acute angle of about 45°. Some twenty 

 or twenty-one oblique, oval, concentric undulations of the surface, distinct but not prominent ; broad, but 

 faint rays, diverging from the umbo to the circumference. 



Relations and differences. — This Inoceramus differs from I. planus, which it most nearly approaches, in 

 being less circular, more convex, more inequilateral, umbos more prominent and gibbous, concentric 

 undulations or folds more regular, angle formed by the hinge and axis more acute. 



From the cretaceous formation on Sage Creek, Nebraska. The nacre of the shell, as well as most of 

 those found associated with it on Sage Creek, is in as good a state of preservation as that of dead shells 

 now on the sea-shore. 



CUCULL7EA NEBRASCENSIS. (N. S.) 

 (Tab. VII., fig. 1, and 1, a.) 



Specific character. — When both valves are united, this shell is heart-shaped or cardiform. The indi- 

 vidual valves are subrhomboidal, oblique, inequilateral, equivalve ; numerous minute, unequal, transverse, 

 concentric stria;; hinge straight, and gently curved upward towards the beaks, which are slightly incurved, 

 and not very distant ; area with seven or eight rhombic furrows (formed by the margin of imbricated 

 lamellae). Transverse, lateral teeth three, both at anterior and posterior side, with three accessory 

 lamellae, the upper and under surface of which are roughened with fine transverse serrations. Central 

 longitudinal teeth irregular. Anterior muscular impression long oval, and bounded beneath by a sharp, 

 shelly projection, posterior rectangular; shell moderately thick. Length (with beak), two inches; 

 breadth the same. 



Relations and differences. — In its general shape this species is not unlike C. transversa, from the 

 eocene tertiary, described and figured by William B. and H. D. Rogers, p. 373, PI. XXIX., fig. 1, Con- 

 tributions to the Geology of the Tertiary Formations of Virginia, Second Scries ; it differs, however, in 

 several essential specific peculiarities ; in the form of the lateral teeth, and their number on the posterior 

 side ; in having no longitudinal strife, and the inner border not being crenulated ; and in having three 

 more furrows on the area of each valve. 



From the cretaceous formation of the Fox Hills, between the Cheyenne and Moreau Rivers. 



