320 



NORTH AMERICAN INDEX FOSSILS. 



Fig. 403. Spirifer- vanuxemi 

 Nat. size and enlarged (Pal. N. Y. 

 VIII.). 



331. S. vanuxemi Hall. (Fig. 403.) Siluric. 

 Small, with rounded extremities. Surface marked by 2 to 4 



broad plications on each side the 

 mesial fold and sinus and by im- 

 bricating concentric growth lines. 

 Differs from 5. crispus in its nar- 

 rower cardinal area, less elevated 

 beak and less gibbous form, and 

 from S. cyclopterns in its smaller 

 size and fewer plications, and from 

 both in its scarcely distinguishable 

 fold and sinus. 



Manlius of New York, Ohio, 

 Michigan. 



332. S. eriensis Grabau. (Fig. 404.) Siluric. 

 Pedicle valve very gibbous and almost square in outline. Car- 

 dinal area high. Sinus and fold sharply de- 

 fined and angular, bounded by a few broad 

 and nearly obsolete plications. 



Cobleskill and Manlius of New York, etc. 



S. corallinensis Grabau. (Fig. 405.) 



Siluric. 

 Very small. Similar to 5. crispus 

 but differing in the uniformly obso- 

 lescent plications and the angular me- 

 dian sinus. 



Cobleskill of New York, etc. 



333 



Fig. 404. Spirifer eri- 

 ensis. ( After Grabau. ) 



I $ 



O 



Fig. 405. Spirifer corallinensis 

 (Pal. N. Y., III.). 



334. S. macropleura (Conrad). (Fig. 

 406.) Devonic. 



Large, ventricose. Valves nearly 

 equally convex. Pedicle valve with broad, deep sinus and three 

 broad, rounded plications on each side. Brachial valve with broad, 

 rounded fold and two rounded plications on each side. Whole 

 surface covered with fine and close radiating striae. 



Helderbergian (New Scotland) of Maine, New York, Maryland, 

 Tennessee. 



335. S. (Delthyris) perlamellosus Hall. (Fig. 407.) Devonic. 



Hinge line more or less extended. Pedicle valve arcuate with 



much extended and incurved beak. Sinus deep and profound, 



