()4 COLORADO COLLEGE STUDIES. 



growth-lines which are crossed by a series of subreniote re- 

 volving^- strijc, the upper centripetal border of the whorls 

 beinu: puckered so as to j^ive it a crenulated appearance; 

 ornamentation of lower surface of shell unknown. 



Measureuients. — Greatest breadth of shell 13.5, height 

 (that of the body- whorl) 4.3, height of cross-section of cavity 

 near aperture 2.5, breadth of same 3 mm. 



Occurrence. — A single specimen of this shell, in situ, was 

 found by the writer in the Comanche Peak limestone on a 

 south branch of Little Hickory creek, a few miles north and 

 a little west of Marietta. Indian Territory. It was associated 

 with Enallasfer tcranus, Volafrcdcrickshurgensis, Turritella 

 seriatim-gramilatd, Tylostoma tumida, and Schloenhachici 

 peruviana. 



Viewed from above, this shell bears close resemblance, 

 even in the oblique and slightly wavy apertural border, to 

 Solarium planorhis, Roenier, as tigured in Palreontologische 

 Abhaudlungen, Band IV, Tafel XXXI; but in apertural view 

 (a section immediately back of the aperture), the body-whorl 

 is seen to be quite different from that species as figured, with 

 respect to shape, thickness of different parts of the section of 

 the shell, and form of the cavity. The apertural view of the 

 present shell does not exhibit that very strongly and equi- 

 laterally compressed form of whorl, with parallel-outlined 

 and uniformly thick- walled cavity, that Roemer's figure rep- 

 resents (fig. 14c, loc. cit.). Indeed, that view of the present 

 shell may be described as intermediate between the figure 

 just cited and that of Eiiomphalus siibquadratus, M. & W., 

 given in Volume V of the Geological Survey of Illinois, PI. 

 XXIX, fig. 13 b, so that it would seem not an unreasonable 

 question to ask, whether the species could not be referred to 

 the genus Slraparollus (which survived till the Jurassic, ac- 

 cording to Zittel), quite as well as to the genus Solarium. 



It may be of interest to know, in comparing Austin rocks 

 with those of the Red river region, that in the same lime- 

 stone, and not far away from the locality that yielded this 

 close ally of Solarium planorhi$, the writer has found one of 

 the specific members of the peculiar Barton creek fauna of 



