IK'.l-ODA. '"' 



U.nr.l.-lU dycrl.l 



tian-vcr..c .liaineter relatively greater, the latter exceeding the vertical diameter by 

 one-sixth, whereas the two >limensions are equal, or the hi^ht the greater, in ' . 

 ti-i>in'inliiri<. r'urthermore, the folds of the surface imbrications are fewer in 

 nunil'er. there being only live or six on each of the dorsal slopes to eight or nine in 

 that -| I li'-n the revolving ridges are more distinct, and the keel is more 



abrupt. e-|.fruii!\ on interior casts of C. </'-""/'X the latter exhibiting distinctly 

 a Imiail furrow on each side of the keel. The slit extends quite half around the 

 last whorl. 



Formation and locality." Glade llmestonr " t.f tin- Stones River irri.up, Lebanon, Tennessee, where 



tin- \\\--* ithri-e specimen* 'I I . 1'nif. J. M. SafTnrd, :unl -c-ni lo one of the authors for 



dwcript 



CONKADKI.LA DYKRt Hall. 

 PLATE I.XVII. I'll. 



CyrtolUt* dyrri II MI., 1871, Advance sheoU, 24th K- -pi. !: V 'lit- N. V. Si. < all., uml it-i-* f same. 



\*~Z, p. 230, pi. viii, flgu. 7, a MKKK. 1873, Pal. Ohio, vol. 1. p. H!, pi. xin. 

 tU'~ nut W and r, thrv r.-pr.-srntint; C'. eiryatu Miller). MII.I.KII, 



1-71, Clnclonatl yuart. Jour. Sri., vol. 1. p. 309. 



1 -null. 10 to 13 mm. in diameter, laterally compressed, consisting of two 

 an. I a half or three volutions, the outer embracing the next within for about one- 

 third of its bight. Whorls cordiform in section, broadest and sharply rounded 

 below, sharply and abruptly carinate dorsally, rounded on the sides the curvature 

 increasing down war.) from the keel; bight and width of volutions, including the 

 .11 ina, about equal, or the former slightly the greater. Umbilicus about equalling 

 the dorso-ventral diameter of the last turn at the aperture. Surface marked by 

 numerous closely and regularly arranged transverse lamelhc, the raised edges of which 

 are curved abruptly backw anl at regular intervals and have a general retral direction 

 from the umbilicus to the keel. The recurved intervals being more prominent than 

 the longer straight portions, and occurring at regular intervals, they cause the 

 surface to appear as having revolving ribs. On the ventral half of the volutions the 

 lower sides of the loops sometimes coalesce and form really continuous revolving 

 lines. Ten of the loops on each -i.U> is the usual number for the last whorl, but two 

 extra ones arc -, mctitnes distinguishable near the aperture of larger examples. Of 

 the transverse lamella- the average number on the back of the last volution in 'J 

 mm. is seven or eight, The keel is prominent, rounded on the summit, and, so far 

 as observed, without a trace of lunula-, although -ome of the specimens before us 

 are in a beautiful state of preservation. The slit has the usual length (i. e., nearly 

 a half volution). 



