ORTHOCERATITES, Breynius. 



O. Blakei, n. s. 



PI. 3, Fig. 1. 



Shell slender, conical ; apical angle in young specimens, 11° ; 

 diminishing as the animal increases in size, so that, in a frag- 

 ment .7 inch in diameter, the sides are almost parallel. Septa 

 placed at two-fifths the diameter of the shell apart. Siphon 

 small, central. Surface plain. 



There are no marked characters by which this species can he well distinguished. 

 All the specimens are small. The figures are natural size. 



Locality: Buena Vista District, Humboldt Mining Region. Collected by Gor- 

 ham Blake, Esq., in honor of whom the species is named. 



NAUTILUS, Breyn. 



N. Whitneyi, n. s. 



PI. 3, Figs. 2, 3. 



Shell moderate in size; last volution expanding somewhat 

 rapidly towards the aperture, enveloping about two-thirds of the 

 preceding whorl. Sides flat, converging towards the dorsum, 

 and gradually rounding into it. Dorsum slightly arched. Um- 

 bilicus large, being nearly one-third the diameter of the whole 

 disk; the umbilical margin slopes outwards and unites with the 

 surface of the shell by a rounded angle. Septa deeply arched 



(19) 



