COLOCERAS COYANUM. 



113 



middle one, which is very prominent (much more so than the drawing indicates — 

 fig. 2 a), curves forward from the border of the umbilical keel, and, taking a 

 course corresponding nearly with the curvature of the hyponomic sinus, becomes 

 obsolete before the centre of the latter is reached. The breadth of the folds 

 nearly equals that of the space between them. Of the inner fold but little 

 remains, as the test is here broken away, and it seems evident that the folds 

 originated in a thickening of the test, there being only a slight trace of them 

 upon the cast. In otlier features there seems to be nothing to distinguish this 

 shell from V. cariniferus, though the septation being covered by the test, its 

 identity with that species is not quite so firmly established as could be wished. 

 The body-chamber, where it is bare of the test, is very distinctly marked on the 

 peripheral part by the " Runzelschicht " (PL XXVIII, fig. 2 b), which consists, 

 as usual, of minute pits, lineally arranged, the lines conforming exactly with the 

 contour of the aperture. The test shows fine lines of growth (seen also in fig. 2 b), 

 somewhat irregularly spaced, and liaving naturally the same direction as those of 

 the Runzelschicht.] 



Famihj Colocehatid.e. 



Genm CohocEBAS, Hijatt, 1893. 



CoLocEitAs CoYANUii, A. d'Orbigiiij, sp. Plate XXX, fig. 3. 



lS4-i. ZSTAUTiLrs (Temnocheilus) pikguis, F. MCoy. Syuop. Carb. Foss. 



Ireland, p. 22, pi. iv, fig. 12 

 {not of L. G. <le Kouinek). 

 18-t7. — HiBEENicrs, A. d'Orhigmj. Paleont. uuivers., toni. i, pi. ci, 



iigs. 2, 3. 

 1850. — CoTANCs, A. d'Orhigny. Pak'out. etratigr., torn, i, p. 111. 



1860. Temnocheilus pinguis, R. Gn'ffitJi. Journ. Geol. Soc. Dublin, vol. ix, 



p. 50. 

 1878. NACTiLrs Coyaxus, Z. G. de Koninck. Faune Calc. Carb. Belgique (Aun. 

 Mu8. Roy. d'Hist. Nat. Belgique, ser. Palscont., 

 toil), ii), pt. i, p. 101, pi. xxxi, fig8. 2, 3. 

 1893. CoLOCEBAS CoTAUtiM, A. Hyatt. Carboniferous Cephalopode. .Second 



paper. Geological Survey of Texas, Fourth 

 Annual Report, 1892, p. -152. 



Description. — Shell tliick-discoid, subglobose, subhexagonal in transverse 

 section until the body-chamber is reached, when the angularity of the sides 

 becomes obsolete ; the inner wliorls exposed in a deep funnel-shaped umbilicus, 



17 



