TRgNTON LIMESTONE. 179 



231. 8. MURCHISONIA PERANGULATA, var. A. 



Pl. XXXVIII. Figs. 7 a, b. 



Subfusiform ; spire elongated, direct, apex sharp ; volutions six or more, close, angular, 

 not ventricose, gradually enlarging below ; mesial angle very prominent, appressed above 

 and below ; mesial band double, as in M. bicincta j surface marked by distinct vertical 

 striae, which make an abrupt retral angle on the mesial band ; aperture not visible. 



This species resembles the M. bicincta in its surface markings, but the volutions are more 

 numerous, and enlarge much more gradually below ; it is also less ventricose, and the 

 upper carina of each volution is nearer the suture. It will probably prove identical with 

 M. perangulata of the Birdseye limestone, which differs only in the absence of the upper 

 carina, which is distinct in this one. 



Fig. 7 a. Back of the spire, showing six volutions 



Fig. 7 b. A portion of the surface, with the stri® enlarged. 



Position and locality. This species occurs, with M. bicincta, in the lower shaly layers at 

 Middleville. 



232. 9. MURCHISONIA UNIANGULATA ( n. sp.). 



Pi.. XXXVIII. Fig. 8. 



Fusiform ; sjiire elongated, rapidly ascending, acute ; volutions about five, angular, the 

 last one ventricose below ; aperture oval, extended below ; surface marked by a single 

 carina upon the centre of the volutions, which are crossed by vertical striae bending back- 

 wards upon the carina. 



This species has the form of the last one, but the volutions ascend more rapidly, and 

 there is but a single carination upon the centre of the volution. The latter character dis- 

 tinguishes it from the other species, which all have a smaller carina near the upper margin 

 of the volution ; and the last whorl has one below the centre, corresponding to the sutural 

 line, which is not seen in the present species. 



Position and locality. This species occurs with the preceding at Middleville. 



233. 10. MURCHISONIA BELLICINCTA (n.*j9.). 



Pl. XXXIX. Figs. 1 a, b, c, rf^e. 



Compare Turritella cingulata. Hisinger, 1837, I,eth. Suecica, pag. 39, pi. 12, fig. 6. 



Pleurotomaria cingulata. Von Buch, 1840, Beitr. zur Geol. Russland, p. 116. 



Murchaonia cingulata. I^Anchiac & Vkkneuil, Bull, de la Soc. g^ol. de France, Vol. xii. p. 459. 



— — MuRCHisoN & Verneuil, Pal. Russia, &.c. 1845, pag. 339, pi. 22, fig. 7 a, J. 



Pleurotomaria. Emmons, Geol. Report, 1842, pag. 390, fig. 6. 



Elongated ; spire composed of eight or more volutions, which are regularly convex, and 

 somewhat rapidly enlarging from the apex ; volutions moderately oblique, marked upon 

 the centre by a flat spiral band, which is margined by slight sharp elevations ; striae bending 



23* 



