STANTON.] AVICULID^E. 81 



small; uinbonal region narrow; beaks prominent, curved forward and 

 inward; test comparatively thin throughout the whole shell, surface 

 having the ordinary concentric lines of growth, and the test is also 

 thrown into numerous rude and irregular concentric undulations. 



u Length of the largest example in the collection, about 22 cm ; great- 

 est breadth, about 15 cm . 



"This species is remarkable for the rudeness and extravagant irregu- 

 larity of the undulations of the surface, of which irregularity the out- 

 line also partakes, giving the shell a flaccid aspect. The specimens of 

 the collection are almost wholly in the form of natural casts, being pre- 

 served in a finegrained calcareous sandstone, some of which is crowded 

 with specimens of this species. 



"Position and locality. — Strata of the Cretaceous period, 5 miles 

 above Pueblo, Colorado." 



This species is not known from any other locality. The only Ameri- 

 can species resembling it in surface features is Inoceramus gilbcrti 

 White, but the form is quite different in the type specimens. 



Inoceramus tjmbonatus M. & II. 



PI. xviii, Figs. 1 and 2. 



Inoceramns nmlonatns Meek and Hayden, 1858, Proe. Acad. Nat. Sci., Phila., p. 50; 



Meek, 1876, U. S. Geol. Sur. Terr., vol. ix, p. 44, PL 3, Figs, la, b, c, and PI. 4, 



Figs, la, b, and 2a, b. 

 Compare Inoceramus involutns Sowerby, 1828, Min. Conch, vol VI, p. 160, PI. 583. 

 Compare also Inoceramus exogyroides M. and H., 1862, /. tenuirostratus M. and H. ; 



1862, and /. capulus Shumard, I860, Trans. St. Louis Acad. Sci., vol. i, p. 606. 



Eevised description : 



" Shell attaining a rather large size, vertically subovate, extremely 

 inequivalve; height more than one-third greater than the anterior- 

 posterior diameter; base regularly rouuded; hinge and interior 

 unknown. Left valve very convex; beak greatly elevated, gibbous, 

 strongly and somewhat obliquely involute, so as to form one and a half 

 to two entire turns, the point terminating near the anterior side; sur- 

 face unknown, that of internal casts sometimes showing faint traces of 

 concentric undulations. Eight valve subcircular, or a little oval trans- 

 versely, much compressed or nearly fiat, excepting in the central and 

 umbonal regions, which are moderately convex; beaks rather oblique, 

 projecting little above the hinge, and but slightly incurved; surface 

 (of an internal cast) ornamented with regular, rather prominent, sub- 

 angular, concentric undulations, separated by wider rounded depres- 

 sions. 



"Height of left valve, about 7 inches; antero-posterior diameter, 

 5-10 inches; convexity, 4-50 inches. Eight valve, height, about 5-70 

 inches; antero-posterior diameter, 5-10 inches; convexity, about 1*60 

 inches. 



Bull. 10G G 



