DESCRIPTIONS OF SPECIES. 



CEPHALOPODA.' 



Nautilus Suciensis. (X. Sp.) 



Plate 11, figures 1 and la. 



Perhaps a variety of Nautilus Albensis, Pictet & Campiche (as of D'Orbigny,) Materi- 

 aux pour la Paleontologie Suisse. Descripticm des fossiles du Terrain Cr6tace 

 des environs de Sainte Croix, Pt. 1, pp. 121 and 134, pi. 17. 



Shell subglobose, broadly rounded on the peripheiy and somewhat 

 compressed at the sides; umbilicus closed, umbilical region shtiUowly 

 concave. Aperture reniform-subluuate, wider than high, deeply eraar- 

 ginate at the base. Measured along the median line, where the emai-gina- 

 tioD is greatest, the height of the aperture is about one-third less than 

 its width, and outside of the emargination the width still slightly exceeds 

 the height. Septa distant, slightly flexuous ; near the umbilical depression 

 they curve abruptly and convexly forwards, then backwards in a much 

 more elongated but shallowly concave curve, which extends over the 

 greater part of the side, after which they cross the periphery in almost 

 straight lines. Siphuncle nearly central, but placed a little on the inner 

 side of the centre of each septum. 



Outer half of the last volution marked by broad, rounded, but much 

 flattened, undulating ribs, which are obsole'.e on and immediately around 

 the umbilical depression, but which are mord strongly marked on and 

 towards the periphery. On the outer portion of the sides they curve 

 boldly and convexly forwards, and in j)assing over the periphery they 

 each run parallel with the broadly concave, but not very deep or angular 

 sinus of that part of the outer lip. Those which are farthest from the 

 aperture are parallel with each other, but those nearer the mouth coalesce 

 obscurely, in an alternate fashion, just before crossing the periphery. 

 Between four and a-half and five ribs can be counted in the length of an 

 inch. The remainder of the surface is either smooth, or else very finely 

 striated across, the striae taking the same direction as the ribs. 



One very well preserved, but somew^hat distorted specimen, (the one 

 fi-ured), and a portion of another, were collected by Mr. Richardson, 



In the classlflcatlon of the MoUusca and Moliuscoidea, the -writer has followed, as nearly 

 as; issible, the order a • pted In the "Arrangemeut of 'he Families of Mollusks, prepared for 

 tbi' ioiichsoiilan iasiituUoa, by Theodore dill, M.D., Ph.D.," puhUshed at vvashlngton In isri. 



