LNVEETEBEATE PALEONTOLOGY. 57 



I ei o <• <* r :i in ns tcnuilineatns. H. & M. 



Plate 12, fig. 6. 



I imn in nui" li iiiiil'iiiiinis. Hall and Meek i 1854 I, Mem. Am. Acad. Arts and Sci., VIII, 387, pi. 'J. li^. :;. n. h. 



" Shell obliquely rhomboid-ovate ; height a little more than two-thirds the 

 length; beaks toward the anterior extremity, elevated, ventricose, and 

 incurved : hinge-line straight, making an angle with the anterior margin of 

 about 10U° ; posterior side extremely elongated and rounded at the extremity ; 

 surface marked by irregular undulations, winch are nearly obsolete on exfoli- 

 ated specimens. A small portion of the external surface remaining near the 

 anterior extremity, shows minute crowded concentric stria?." 



The depressed, transversely-ovate form, nearly smooth surface, and 

 oblique, prominent, gibbous beaks of this species, will distinguish it from all 

 the others resembling it in other respects, yet known from the Cretaceous 

 rocks of this region. It appears to be a rather thin shell. The points of 

 the beaks are generally elevated little above the hinge; though the swell of 

 the umbones a little farther back rises rather distinctly above it Between 

 this convex umbonal region and the hinge, there is usually a broad, rounded 

 depression in casts. The specimens yet obtained are so much mutilated 

 that I have preferred to give a copy of the original figure. It seems to be 

 a well-defined species. 



Localiti/ awl position. — Great Bend of the Missouri; in lower part of 

 Port Pierre group of the Cretaceous series; and at Sa_ r e ('reek, in the upper 

 beds of the same formation. 



I ii o c c r a m u s Vaimxcmi/M. & H. 



Plate 14, tigs. 2, a, b. 

 lnoceramus Vanuxemi, Meek and Hayden (May. 1H60), Proceed. Acad. Nat. Sci. Philad., Ill, 180. 



Shell large, subcircular, much compressed ; anterior side broadly-rounded, 



and shorter than the other; base forming a nearly semicircular curve, being 

 a little more prominent behind thaft in front ; posterior side wider than the 

 other, broadly rounded or subtruncated : Inline short, straight, and forming an 

 angle of about 90° with the vertical axis of the valves ; beaks very small, 

 compressed, and scarcely rising above the hinge, not distinctly incurved, 

 located a little in advance of the middle Surface ornamented by regular, 

 8 H 



