LOWER HELDERBERG ROCKS. S09 



Trematospira multistriata ( n. s.). 



Plate XXIV. Fia. S a-t; and Plate XXVIII A. Fig. 5 a-/. 

 Spirifer multistriatus : Hall, Descr. New Species Pal. Fossils, in Regent's Eeport, etc. 1856. 



Shell transversely oval or subrhomboidal, with angles rounded : hinge 

 line slightly declining on each side of the centre ; cardinal extremities 

 rounded. Ventral valve moderately convex towards the beak, with a 

 broad not sharply defined sinus below, which often becomes obsolete 

 before reaching the beak : beak perforate, abruptly incurved over the 

 opposite. Dorsal valve the more convex, the middle elevated in a broad 

 scarcely defined lobe : beak closely incurved beneath the other, filling 

 the foramen in the ventral valve. Area narrow, strongly striated lon- 

 gitudinally. 



SuEFACE granulose or punctate, and marked by numerous fine striae which 

 bifurcate once or oftener between the beak and base of the shell, 

 crossed concentrically by imbricating lamellae of growth. 



•This species was originally described as a Spirifer, from having the appearance 

 of an area, and which is sometimes enhanced by the partial displacement of the 

 valves. A separate valve, fig. 3 u, shows obscurely some characters of the ventral 

 valve of Spirifer. The junction of the valves and absence of a true area, as well as 

 the insertion of the beak of the dorsal valve beneath the opposite, are well shown 

 in several of the figures. 



Fig. S a - t. Illustrations showing gradation of size, variety of form, etc. 

 Fig. 3 y. Enlargement of the strise. 



PLATE XXVIII A. 



Fig. 5 a. An individual of medium size, having the beaks closely incurved, and without 

 indication of an area. 



Fig. 5 b. Dorsal view, where the minute perforation in the beak of the ventral valve is bare- 

 ly seeli above the summit of the opposite one. 



Fig. 5 c, d, e. Ventral, front, and profile views of the same individual. 



Fig. 5 f. The interior of a ventral valve, showing the remains of internal spires. 



Geological position and locality. In the ^aly limestone of the Lower Helderberg 

 group : Helderberg mountains, Schoharie, etc. 



[ PAL.aB0NTOLOaY III.] 27 



