NATURAL SCIENCES OF PHILADELPHIA. 49 



by the breaking away of a thin part of the matrix between the uiphuncle and 

 the outer shell. None of our specimens are in a condition to show the mar- 

 gins of the lip, but some of them show very clearly the commenoemenl of the 

 protuberance, or pinching up of the margin on each side near the umbilicus 



evidently terminating at the aperture in the usual spout-like auricles. The 

 lines of growth also show the same, by their flexures on each side. 



Specifically this shell is probably most nearly allied to our N. (Solenoek 

 Leidyi, from the Keokuk division of the Lower Carboniferous, though it differs 

 in having more rapidly expanding and subquadrangular whorls, which are 

 also slightly embracing at the aperture, instead of being merely in contact. 

 Its volutions, however, are much less rapidly expanding than in 'our X. (& 

 capax, or in N. Springeri ot White and St. John, as well as different from both 

 in their subquadrangular form. 



Locality and position. New Providence, Indiana, from a limestone of the age 

 of the St. Louis division of the Lower Carboniferous. 



Subgenus TEMNOCHILUS, McCoy. 

 Nautilus (Temnochilus) latus, M. and W. 



Comp. N. nodocarinatus, M'Chesney, 1865. Illustrations Paleozoic Fossils, 

 pi. 3, fig. 6 (5 by error, in explanations of plate.) Not N. nodocarinitus of 

 same author in text of same paper (1860) p. 66. 



The only specimen of this fine species we have ever seen consists of about 

 half of one volution, which, being without septa, must belong to the part 

 composing the last or body chamber, originally occupied by the body of the 

 animal. Tt 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 distinctly flattened 

 space between. Along each (so-called) dorso-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 regu- 

 larly into the umbilicus, which appears to be wider than the dorso-ventral 

 diameter of the volution at the aperture. The surface is without longitudinal 

 lines, but the strhe of growth are moderately distinct, especially on the broad 

 flattened outer side, where they make a deep backward curve in crossing, so 

 as to indicate the presence of a very deep sinus in the lip on that side of the 

 aperture of the shell. 



In the specimen described, the substance of the shell is thin, and scarcely 

 mineralized, though it retains no pearly lustre. 



This species resembles very closely the form figured by Prof. McChesney in 

 the memoir cited at the head of the foregoing description, and referred by 

 him (by mistake) in the explanations of his plates, to his N. nodocarinatus. 



Our shell differs, however, in not having so many nodes, as well as in hav- 

 ing a proportionally wider umbilicus, and particularly in having the sides of 

 itswhorls rounding regularly into the umbilicus, instead of being subcarinate 

 around its margins. 



Locality and position. Carbon Cliff Mines, Rock Island. County, Illinois. 

 Lower Coal-Measures. 



1870.] 4 



