Geol.— Vol. II.] ANDERSON— CRETACEOUS DEPOSITS. II 7 



b}' Gabb can hardly be made to agree with those of Trask 

 (1. c). The description of neither species can be consid- 

 ered satisfactory; yet enough is shown and told to make it 

 evident that two species, and not one, have been described 

 under this name. 



In Trask's species there are about twenty-four distinct 

 and simple ribs, bearing a double row of tubercules near 

 the outer margin of the coil. The ribs do not bifurcate 

 upon the sides, but seem to consist of two kinds, primar}- 

 and auxiliary. The latter do not extend to the umbilicus, 

 but disappear a little above the middle of the sides, and 

 extend to the outer margin. No statement is made as to 

 the relative size of the umbilicus, but in Trask's figure it 

 appears to be more than one-third the diameter of the 

 entire coil. The section of the whorl is oval rather than 

 flattened, as in Gabb's species. 



The specimen figured by Trask was probably an imma- 

 ture one, and there is room for a considerable change in 

 these features during a more complete growth; yet the 

 changes would hardly be of the nature which Gabb's 

 figures indicate. There is in the collections at Berkeley a 

 small specimen, labeled as coming from Trask's original 

 locality, which agrees tolerably well with his description 

 except in the number of ribs, which is slightly greater. 

 Trask's species also seems to be much less common than 

 Gabb's, or it has not been definitely recognized. 



Occurrence. — Trask's specimens came from the Upper 

 Chico, on the eastern side of the Sacramento Valley, and 

 from the locality of Chico Creek, and Pence's ranch, 

 California. 



63. Schloenbachia gabbi, sp. nov. 



Ammonites chico'ensis Gabb (not Trask). Paleontology' Cal., Vol. I. p. 68, 

 Pis. XVIII-XIX. 



In the collections of the University of California are 



several well-preserved casts of Gabb's species of this shell 



from the original localities of both Trask and Gabb. They 



are identifiable without great difficulty from Gabb's figures 



and description, with which they agree fairly well in most 



points. 



(9) December 22, 1902. 



