(510 PALEONTOLOGY OF ILLINOIS. 



defined lines of growth, which curve gently backward in 

 crossing the sides of the whorls from the inner margin, and 

 make a strong backward curve in crossing the periphery, 

 so as to indicate the presence of a deep rounded sinus in 

 the outer margin of the lip. (Siphuncle and septa un- 

 known.) Greatest breadth of a specimen with a part of 

 the outer volution broken away, 4.60 inches; transverse 

 diameter of outer turn, measuring across the periphery 

 without including the nodes, 2.46 inches; do., including 

 the nodes, .2. 95 inches; dorso- ventral diameter of the outer 

 volution, 1.66 inches. 



This species is evidently closely allied to the last in form and general 

 appearance, but differs in having its volutions proportionally narrower, 

 measuring at right angles to the plane of the shell. Its most marked 

 difference, however, consists in the form of its nodes, which are round, 

 instead of being distinctly compressed. It seems to be related to N. 

 tuberculatus, of Sowerby, but differs from the published figures of that 

 species in having its periphery proportionally broader, and distinctly 

 more flattened, while its nodes are placed nearer the outer margin of 

 the whorls, as well as more prominent. From N. occidentals, of Swal- 

 low ( N. quadranyularis, McCbesney,) it will be readily distinguished 

 by the greater transverse diameter of its whorls, which are also with- 

 out the flattened sides of that species, and differs in wanting the two 

 mesial rows of nodes on the periphery. 



The specific name of this fine Nantilm is given in honor of Dr. J. (J. 

 WINSLOW, of Danville, Illinois, to whom we are indebted for the use 

 of the specimen from which the description was drawn up. 



Locality and position Danville, Illinois. Roof shales of Goal No. 7 

 of the Illinois section of the Coal Measures. 



NAUTILUS LASALLEKSIS, M. and W. 



PL 31, Figl. 

 Nautilus Lasallensig, MEEK and WOKTHEN, 1866. Proceed. Acad. Nat. Sci., Phila,, for Dec., 1865, p. 261. 



SHELL attaining a medium si/e, sub-discoidal; umbili- 

 cus more than half as wide as the dorse-ventral diameter 

 of the last whorl at the aperture, moderately deep, and 

 showing about half of each inner turn. Yolutions increas- 



