CRETACEOUS FOSSILS. 437 



TECTIBRANCHIATA. 



BULLIDM. 



Genus HAMINEA Leach. 

 HAMBTEA SUBCYLINDRICA. 



Plate 12, fig. '24. 



Bulla subcylindrica M. & H., Proc. Acad. Nat. Sci. Phil., vol. 8, p. 270 (not of D'Orb., 1847). 

 Bulla speciosa (M. & H.) Meek, Smithsonian Check List Invei t. Foss., p. 16, Proc. Acad. 



Nat. Sci. Phil., vol. 12, p. 185. 

 Haminea subcylindrica (M. & H.) Meek, U. S. Geol. Surv. Terr., p. 272, PI. 18, fig. 10. 



Shell of moderate size, elongate-oval or slightly ovate in form, with 

 rather sharply rounded extremities; upper end marked with a small central 

 umbilical pit or depression indicating the position of the sunken spire, and 

 the outer volution elevated but little above the preceding one; lower 

 extremity somewhat extended and narrowly rounded from the short, slightly 

 curved, columellar-like inner lip around the base of the aperture; aperture 

 very narrow above but gradually widening below, and strongly arcuate 

 throughout: outer lip thin and sharp, lower umbilical slit minute. Surface 

 of the shell marked by fine impressed revolving lines, many of which have 

 a somewhat alternating character, and are crossed by finer concentric lines 

 of growth. 



The shells of this species which we have in hand are none of them entire 

 or full grown, but their specific features are well marked. It is the only one 

 of the group we have noticed in the collection, although several others 

 have been described from the Cretaceous formations of this region. It is 

 readily distinguished from the others by the form of the shell. 



Formation and locality. — In limestones of the Fort Pierre' Group, on 

 Old Woman Fork of the Cheyenne River, Black Hills. 



Genus AKERA 0. F. Muller. 



AKERA GLANS-ORYZA. 



Plate 12, fig. 25. 

 Altera glans-oryza Whitf., Prelim. Rept. Pal. Black Hills, 1877, p. 38. 



Shell minute, not exceeding one-fifth of an inch in length, and the 

 diameter being about twice and a half less than the length; cylindrical in 



