I04 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



men brought from Vancouver Island, and represents 

 neither A. siiciaensis nor A. tnerriami ; yet perhaps they are 

 related. 



The type represented by Gabb's figure, however, has 

 actually been found in the Lower Chico beds of the 

 Oregon basin, at Henley, Siskiyou County, and is de- 

 scribed in the following pages as Pachydiscus henleyensis. 



Occurrence. — Pachydiscus merriami belongs near the top 

 of the Horsetown horizon. Three samples, representing 

 successive stages in its growth, were obtained from the 

 Upper Horsetown beds of Hulen Creek, Shasta County, 

 California. 



The types are in the collection of the University of Cali- 

 fornia. 



49. Pachydiscus henleyensis, sp. nov. 

 Plate VIII, Figs. 165-166. 



Ammonites sucia'ensis Gabb (in part). Pal. Cal., Vol. I, Pis. XXVII and 

 XXVI II. 



Shell robust, inflated, section of whorl broader than high, being reniform, 

 the ratio approximately nine to five; the umbilicus narrow, with rounded 

 shoulders; surface crossed by low, rounded ridges flattening and growing 

 in number toward the ventral side; sides of young shell moderately even, 

 and rounded in section, but flattening with age and breaking up into broad 

 undulations which appear to arise with growth from heavier ribs placed at 

 intervals, hardly noticeable on shells below a diameter of 15 centimeters. 

 The suture line is well represented by Gabb's figure, the lobes being narrow 

 and exceedingly divided. 



Gabb's figure of this species is from a specimen about 

 five and one-half inches in diameter, a size intermediate 

 between the two that are represented in the sections given 

 for P. henleyensis. The section published by Gabb is evi- 

 dently not accurately drawn, showing too great an involu- 

 tion. A correction of this error shows the section of 

 Gabb's specimen to be intermediate to those given here, 

 which were both drawn from one specimen at different 

 ages. 



Occurrence. — Two specimens of this shell were found 

 at Henley, Siskiyou County, California, in the Lower 



