1G6 COLORADO FORMATION AND ITS INVERTEBRATE FAUNA, [bull. 186. 



more numerous and smaller costse without nodes, and by its larger 

 size. 



Locality and position. — From the lower part of the Niobrara lime- 

 stone on Turkey creek, Huerfano park, Colorado, where it is associated 

 with Buchiceras swallovi, Baculites gracilis! and Tnoceramus fragilis. 



Genus BACULITES Lamarck. 



Baculites gracilis Slmmardf 

 PI. xxxvi, Figs. 1-3. 



Baculites gracilis Slmmard, 1860, Trans. St. Louis Acad. Sci., vol. I, p. 596. 

 Baculites ovatus (Say) White, 1876, U. S. Geog. and Geol. Sur. West 100th Meridian, 

 vol. iv, p. 199, PI. 19, Figs. 4& and c. 



Shell small, very slender ; transverse section varying from broad ovate 

 to subelliptical ; surface sometimes nearly smooth, but usually with 

 numerous distinct rounded costre or undulations that are strongest on 

 the siphonal side from which they curve backward parallel with the 

 lines of growth, gradually becoming fainter and disappearing before 

 reaching the opposite side. In addition to the costae there are broad, 

 rather obscure constrictions at intervals of about half an inch that com- 

 pletely encircle the shell. They are also more distinct on the siphonal 

 side and are parallel with the lines of growth, passing nearly straight 

 across the siphonal and antisiphonal sides and curved sharply backward 

 on the flank. 



Septum with six lobes and six saddles, all of the latter, excepting the 

 antisiphonal one, symmetrically but not deeply divided ; lobes much more 

 slender than the saddles. 



Length of the longest fragment in the collection, 10G mm , diameters of 

 the extremities, 10 ,nm by 7£ nim and 5 mni by 4 mm , respectively. 



This species differs from Baculites ovatus in its smaller size and more 

 slender form, in the character of the surface ornamentation, and the 

 details of the septa. The latter have the same general character in the 

 two species, but on comparing specimens of the same size it is seen that 

 in B. gracilis the septa are more distant and not so deeply incised and 

 the lobes are narrower in proportion to breadth of the saddles. 



The fossils above described include the specimens from southeast of 

 Paria, Utah, that were doubtfully referred to B. ovatus by Dr. White 

 (loc. cit.), a larger collection from L T pper Kauab, Utah, where it is asso- 

 ciated with many species of the Colorado formation about 350 feet 

 above the base of the Cretaceous section, and several examples from the 

 Niobrara limestone on Turkey creek, Huerfano park, Colorado. 



Shumard's types were found on Shawnee creek, Grayson county, 

 Texas, in strata that are believed to be approximately the equivalent 

 of the Colorado formation. The species was not figured and I have 

 never seen any Texas examples of it. Consequently the identification 



