504 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



15 <• I c 111 n i i <• I I :i bulbosa, M & H 



Plate 33, figs. 2, a, b, c, d, e, 



Belimmitella bulbosa, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Pbilad., VIII, 70; and ib., 280.— 

 Meek (1864), Smithsonian Check-List N. Am. Cret. Fossils, 'jr.. 



Shell or guard small, slender, subcylindrical, sometimes slightly expanded 

 at the open anterior end, and pointed at the other extremity; vascular 

 markings not very strongly defined, and rather irregular; dorsal ridge mod- 

 erately distinct; alveolar cavity apparently less than half the length of the 

 guard, terminating behind in a minute bulb. Phragmocone tapering regularly 

 at an angle of 20° ; section slightly oval ; substance extremely thin, distinctly 

 pearly, and marked on the surface by scarcely visible, very fine lines of 

 growth, which curve abruptly forward on the dorsal side ; septa separated 

 by spaces about one-sixth their greater diameter, faintly waved forward on 

 the dorsal side. 



Length of a specimen, retaining apparently less than half the alveolar 

 cavity, 2.30 inches ; breadth at the larger (anterior) end, 0.29 inch. 



This species resembles young specimens of B. mucronata, Schloth , but 

 is smaller and more slender than the average-sized adult individuals of that 

 species. It is also more regularly tapering at the lower extremity, though 

 never abruptly attenuated at the immediate point, as we usually see in B. 

 mucronata. The conical cavity in its anterior end seems to be likewise pro- 

 portionally shorter, and differs in having a minute bulb at the extremity. 

 This latter character occurs in other species, though I have not been able to 

 find it in any of the specimens of B. mucronata, from New Jersey or else- 

 where, yet examined. Again, the axial line in our species seems to be always 

 very nearly central, while in B. mucronata it is eccentric. Ours is also an 

 extremely rare species, while B. mucronata is very abundant at most locali- 

 ties where it occurs. 



I am indebted to the Academy of Sciences of Saint Louis, Missouri, for 

 the use of the specimen figured on plate 33, none of our own being in a con- 

 dition to show very clearly the form and surface-markings of the guard. It 

 was presented to the academy by Colonel Vaughan, United States Indian 

 x\gent. 



Locality and position. — Near Moreau trading-post, Dakota; from the 

 Fox Hills group of the Upper Missouri Cretaceous series. It is very rare, 

 only a few specimens having been brought in among all the extensive col- 

 lections from the Northwestern Territories. 



