22 PALAEONTOLOGY OF CALIFORNIA. 



referred to the present one, — some specimens of which must have been a foot in 

 diameter. From their state of preservation, however, it is impossible to decide 

 on their identity, since they only occur as indistinct impressions on slate. Dr. 

 Horn has more recently sent me a specimen, undoubtedly belonging to this spe- 

 cies, found opposite the military station in Owen's Valley, Tulare County, Cali- 

 fornia, about thirteen miles north of Owen's Lake, in the foot-hills on the east 

 side of the valley. 



CERATITES, De Haan. 



C. Haidingerii. ' 



PI. 5, Figs. 8 and 10; and PI. 4, Fig. 9. 

 {GoniatUes Haidingerii, Hauer, Naturwiss., p. L'G4, pi. 8, figs. 9-11.) 



Shell compressed, lenticular. In the young state, the whorl 8 

 entirely enveloping each preceding one; sides slightly arched, 

 converging towards the dorsum, and then suddenly rounding 

 towards it. Dorsum acutely carinate. Umbilicus very small. 

 Aperture emarginate for nearly half its length. Septum, in a 

 specimen about an inch in its greatest diameter, composed of a 

 dorsal and seven lateral lobes. 



More advanced individuals show a strong modification of these 

 characters. In one, having the last whorl with a width of two 

 and a quarter inches, the sides appear to be flatter, the umbilicus 

 is proportionally larger, exhibiting a portiou of some of the inner 

 volutions, the dorsum has lost its central ridge, and becomes 

 strongly bicarinate, and the lateral lobes of the septum are double 

 in number those of the small specimen figured. 



The septum consists, as remarked above, of a variable number 

 of lobes and saddles. The saddles are simply rounded, though 

 sometimes irregular; the larger lobes end abruptly, are deeply 

 notched in the middle, and have one or two teeth on each side of 

 the notch. In young specimens, the lobes nearest the dorsal 

 margin are longest and widest, and show the denticulate termi- 



