Maryland Geological Survey 401 



Length 1.5 cm.; width 1.8 cm. 



This variety differs from the typical fonn in having a well-developed 

 sinus and mesial fold and much more pronounced plications. 



It also resembles S. vanuxemi var. prognosticus, but differs from the 

 latter in its much greater size and absence of spiniferous surface. 



Occurrence. — Helderberg Formation, Keyser Member. Keyser, 

 West Virginia. 



Collection. — Maryland Geological Survey. 



[Maynard.] 



Spirifer octocostatus Hall 

 Plate LXVIII, Figs. 25-29 



Spirifer octocostatus Hall, 1S57, 10th Ann. Rept. N. Y. State Cab. Nat. Hist., 



p. 62. 

 Spirifer octocostatus Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 205, pi. 



xxviii, figs. 4a-e, 1861. 



Description. — " Shell subglohose : valves nearly equally convex. Ven- 

 tral valve most elevated near the beak: sinus angular, extending to the 

 apex : beak slightly incurved. Dorsal valve most convex in the middle : 

 mesial elevation not prominent : beak rising little above the hinge-line, 

 slightly incurved; hinge-line less than the width of the shell, rounded at 

 the extremities. Area triangular, faintly defined, somewhat arcuate. 

 Foramen narrow; a strong median septum dividing the nmseular area, 

 and extending to the apex of the foramen. Surface having about four 

 rounded moderately prominent folds on each side of the mesial sinus and 

 elevation, which become obsolete towards the beaks ; concentrically marked 

 by fine, regular, closely arranged imbricating lamellose strige." Hall, 1859. 



Length 1.5 cm.; width 2.2 cm. 



The species Weller describes as Spirifer octocostatus in the Coeymans of 

 'New Jersey ' is not well preserved, and it is probable that he had another 

 form. 



At Cash Valley and the section If miles northeast of Flintstone and at 

 Hyndman, Pennsylvania, there is a species which has been identified as 

 Spirifer octocostatus. It differs from the normal 5*. octocostatus in having 



' Geol. Survey N. J., Pal., vol. iii, 1903. p. 288, pi. xxx, figs. 5-8. 

 26 



