Tl6 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



An important addition to the number of species of 

 SchlcBiibachta^ hitherto known from the West Coast will be 

 recognized in this paper. No less than ten distinct forms 

 have been found in the Chico beds of Northern California 

 and Southern Oregon. It is possible that with further 

 searching still others will be discovered, since each new 

 collection of them contains some new species not met with 

 before. 



In the Lower Horsetown beds representatives of this 

 genus have not been found, but in the Upper Horse- 

 town is the Cenomanian species, S. injlata. In the Upper 

 Chico are S. chicoensis Trask, S. gahbi, sp. nov. and 

 S. buttensis, sp. nov. By far the larger number, however, 

 are found in the Lower Chico beds, and principally in the 

 Oregon basin. With the exception of a single species, 

 S. chicoensis, there is but little resemblance between those 

 of the two adjoining basins. 



Most of the species described in this paper fall without 

 much question into the genera recognized by Zittel in his 

 later work.^ Four of the genera are represented by two 

 or more species each. There are other forms, however, 

 that admit of such grouping with more difficulty. In some 

 of them the keel entirely disappears in old age, or even 

 before mature age is reached. 



62. Schlcenbachia chicoensis Trask. 



Plate I, Figs. 21-22; Plate II, Figs. 23-25. 



Ammonites chicoensis Trask, Proc. Cal. Acad. Sci., Vol. I, 1856, p. ^, 

 PI. II. 



From a careful study of this species with others nearly 

 related, it is evident that there has been a confusion enter- 

 tained by some of the earlier writers upon the paleontology 

 of California. The figures and description of this species 



^Schlcenbachia is used in this paper in the broad sense originally defined by Zittel in 

 his "Traits de Paleontologie," 18S7. 



""Grundziige der Palreontologie," 1895. 



