DESCRIPTION OF SPECIES 271 



WbitiielcTs description. "Shell of median size, and consisting of 

 aboiit two and a half or three closely coiled volutions, but which are 

 not at all embracing; the outer one being simply in close contact with 

 the medio-dorsal portion of the next within, and exposing nearly the 

 entire dorso- ventral diameter of the shell. Volutions transversely 

 subpentangular, being angularly convex on the back, strongly subangular 

 on the sides and concave on the abrupt umbilical slope, which forms 

 a somewhat sigmoidal curve resembling an ogee molding, while the 

 slightly concave ventral surface is quite narrow, and forms a fifth 

 surface. Lateral angles obtuse or round subangular, and ornamented 

 by a series of nodes which are strong and very distinct on the inner 

 coil, broad and rounded on the first part of the last volution and be- 

 come obsolete on the outer third. The substance of the shell has been 

 very thick and strong, and the surfac3 shows no evidence of growth 

 markings or striae. Septa and other internal features unknown." 



Remarks. Two specimens from the Lower Mercer limestone of 

 Muskingum County have been referred to this species; although the 

 better specimen is imperfect, nevertheless characters similar to those 

 of Whitfield's species are preserved with sufficient distinctness, so that 

 the identification can be made with a considerable degree of confidence. 

 This specimen was found projecting from a loose block of limestone in 

 the bed of Blunt Run, and the surface has consequently suffered some- 

 what from weathering. However, the nodes on the lateral angles are 

 retained with sufficient distinctness to indicate their similarity in form, 

 proximity, and position to Whitfield's species. From a small portion 

 near the end of the last volution they are apparently wanting, while 

 on the inner coil they are strongly marked and closely arranged. Septa 

 not shown. 



The second specimen is referred to the same species much less 

 confidently. It consists of a fragment of one and one-half volutions 

 in a poor state of preservation. Apparently it could be referred almost 

 equally as well to Temnocheilus forbesianus although the lateral nodose 

 angles are situated too close to the impressed zone and the intervening 

 area is too abruptly sloping. However, these differences may have 

 been produced by lateral compression. 



Horizon and locality. Lower Mercer limestone : Muskingum 

 County, Blunt Run, Locality 27, r; Symmes Creek, Locality 29, r. 



Genus Temnocheilus McCoy 

 Temnocheilus forbesianus (McChesney) 



1860 Nautilus forbesianus. McChesney, Desc. New Pal. Foss., p. 63. 



Coal Measures: Mercer County, Illinois. 

 1865 Nautilus forbesianus. McChesney, New Spec. Foss.. PI. 3, Figs. 4a-b. 



