(JON PALEONTOLOGY OF ILLINOIS. 



Genus OHTTCXN", Linnaeus. 

 CHITON CARBONARIUS, Stevens. 



PI. 29, Fig. 15. 

 Amer. Jour. Sci., 1859, Vol. 25, new series, p. 264. 



Position and locality Roof of the Danville coal, Danville, Illinois. 



CEPHALOPODA. 

 NAUTILUS (TEMNOCHILUS) LATUS, M. and W. 



PI. 30, Fig. 2. 

 Nautilus (Temnochilux) latua, MEEK and WOKTHEN, 1870. Proceed. Acad. Nat. Sci., Phila., p. 49. 



THE only specimen of this fine species we have ever seen 

 consists of about half of one volution, which, being with- 

 out septa, must belong to the part composing the last or 

 body chamber, originally occupied by the body of the ani- 

 mal. It is broken at both ends, and measures around the 

 curve of the outer side, 8.50 inches, with, at the larger end, 

 a dorso-ventral diameter of 2.10 inches, and a transverse 

 diameter (including the nodes) of 3.60 inches. The dorso- 

 ventral diameter at the smaller end is about 1.60 inches, 

 and the transverse about 2.40 inches. A section of the 

 body volution is transversely subelliptical, with a tendency 

 to an oblong outline; the outer (often called the dorsal) 

 side of the whorl being very broad and flattened convex, 

 and each lateral margin, exclusive of the nodes, being 

 rather narrowly rounded, or a little flattened, while the 

 inner side is a little concave. The broad flattened outer 

 side has two very obscure longitudinal ridges, with a dis- 

 tinctly flattened space between. Along each (so-called) 

 dorse-lateral margin there is a row of prominent flattened 

 nodes, arranged at intervals of about their own greater 

 (antero-posterior) diameter. About sixteen of these nodes 

 occupied each side of the outer or last volution. The inner 

 side of the whorl rounds regularly into the umbilicus, 



