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



age; in young adult shells the walls of the umbilicus are abrupt, but are 

 more sloping in younger, and more rounded in older shells ; the involution 

 is moderate, one-half of each earlier whorl being covered. The ribs are 

 mostly simple, only a few showing a disposition to bifurcate near the 

 umbilical shoulders. Two-thirds or more of the ribs do not extend to the 

 umbilicus, but arise from the middle of the side, or near the periphery, and 

 cross the ventral surface, curving forward so as to produce an angle on the 

 median plane. In age the ribs mainly disappear, or are reduced to about 

 ten or twelve rounded ridges that are confined to the umbilical side of 

 the whorl. The external side is then rounded and smooth. The diameter 

 of the two largest shells found was about 25 cm. 



This species seems to be somewhat related to Puzosia 

 darwini, as figured by Steinmann, from the Island of 

 Quinquina, The constrictions that are shown upon Chile- 

 an species, however, do not appear upon the casts of the 

 one from Oregon. 



Occurrence. — Several specimens of this shell, one of 

 which is the type, were found four miles southeast of Ash- 

 land, Oregon. A similar shell that may belong to the 

 same species was found at the Forty-nine Mine in Southern 

 Oregon. 



The type of this species is in the collections of the Cali- 

 fornia Academy of Sciences. 



46. Holcodiscus, cf. H. theoboldianus Stol. 

 Plate V, Figs. 126-127; Plate X, Fig. 197. 



In the Voy Collection at the University of California is a 

 beautiful, well preserved specimen of an Holcodtsctis that 

 very closely resembles the above species from the Tri- 

 chinopoly group of Southern India. It belongs to the type 

 of Ammonites incertus d'Orbigny, which comes from the 

 Lower Cretaceous of Europe. Its sculpture exactly agrees 

 with Haploccras cumshewaense Whiteaves, though its form 

 is rather thicker. In this specimen the ratio of width of 

 the whorl to height is about nine to one; in H. cumshewaense 

 the ratio is said to be little more than five to one. 



The shell in the Voy Collection has a diameter of about 6 cm., which is a 

 little more than three times the width of the umbilicus. The umbilicus has 

 abrupt though not vertical walls, the involution exposes about one-half the 

 (8) December 12, 1902 



