I02 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



side of the earlier whorls, the surface is ornamented with numerous fine trans- 

 verse ribs which bifurcate about the middle of the side, or more often one-third 

 of the distance from the umbilicus to the periphery. The ribs extend down- 

 ward on the walls of the umbilicus, are only slightly inclined forward, and 

 but little flexuous. The last whorl is crossed by five rather deep and 

 rounded grooves, marking former positions of the mouth. These grooves 

 follow the direction of the ribs, yet from their posterior margin three or four 

 ribs arise at intervals and cross the periphery. This gives the constrictions 

 an oblique appearance, yet on their anterior side they are exactly parallel to 

 the next succeeding ribs. The grooves are bordered by ridges a very little 

 stronger than the ribs ordinarily, and the anterior one forms a sharp promi- 

 nence where it crosses the umbilical shoulder. The suture line is quite 

 complex, consisting of four or more bifid saddles, very finely divided, ter- 

 minating in rounded denticles, and diminishing regularly in size toward the 

 umbilicus. The trunk and branches of the trifid lobes are relatively wider 

 than the corresponding parts of the saddles, and terminate in pointed, finger- 

 like teeth. The auxiliary lobes have an oblique direction, and are relatively 

 wider than the main, or first lateral lobe. The suture line agrees very well 

 with Stoliczka's figure in the main, but the dissection of the saddle is more 

 complete. 



Occurrence. — It is unfortunate that this interesting spe- 

 cies cannot be more definitely located than a general refer- 

 ence to Cottonwood Creek, Shasta County, California. 

 The sandy character of the matrix, however, suggests that 

 it probably comes from an upper horizon of the Cretaceous 

 section of that place. 



47. Pachydiscus newberryanus Meek (not Gahh). 



Ammonites newberryanus Meek. Trans. Albany Inst., Vol. IV, 1857, 

 p. 47; Bull. Geol. Sur. Terr., Vol. II, 1876, p. 367, PI. IV, figs. 3, 3a, 

 3<5. VVhiteaves, Mes. Foss., Vol. I, 1879, p. 109, PI. XIV. 



Afnmonites fraterniis GhBH, Pal. Cal., Vol. II, PI. XXIII. 



In the collections of the University of California are two 

 or three specimens of this species from Pence's ranch, 

 Butte County, California. These were carefully compared 

 with a typical specimen from the Sucia Islands, in the 

 Straits of Georgia, British Columbia, borrowed from the 

 collections at Stanford University. 



The normal development of this shell is characteristic. In youth, at a 

 diameter of three to four centimeters, the section of the shell is almost circu- 

 lar, though involute to the extent of covering nearly one-half the earlier 

 whorl. The ribs are simple or obscurely bifurcated in part; half of them 



