8 66 
PALEONTOLOGY OF NEW-YORK. 
Ortliis tulmiostriata (n. s.). 
Plate XI. Fig. 1-6. 
Shell circular : valves nearly equally convex, depressed near the margin. 
Ventral valve more prominent towards the beak, which is sharply 
incurved over the area : area narrow, and about half as long as the 
width of the shell. 
Surface striated. Strife somewhat tubular, prominent, fasciculate, in¬ 
creasing by implantation and bifurcation, extremely curved towards 
the margins, and presenting at somewhat regular intervals small tubular 
pore-like openings upon the surface : radiating striae, when not worn, 
crossed by prominent concentric striae, and, rarely, by stronger lines 
of growth. 
Cardinal process of the dorsal valve large, and nearly filling the foramen : 
brachial processes long, slender and diverging. Area of the muscular 
impressions in the ventral valve not strongly defined. 
This species is readily distinguished from the preceding, and from others of similar 
form in these strata, by the prominent fasciculate striae in which the tubular open¬ 
ings are very conspicuous. It may be compared with O. neglecta of I! arrange 
( Silurische Bracliiopoden aus Boehmen : Naturwissenschaftliche Abhandlungen, 
Tab. xi, f. 11); but the figures given by that author represent the area as very dif¬ 
ferent. It is unlike any other form at present known to me in the Silurian rocks of 
the United States. 
Fig. 1-4. Young individuals of this species. 
Fig. 5, 6. Larger individuals. The two figures on each side of fig. 6 are enlargements of 
striae, one without the tubular openings, and the other showing this character. 
The righthand figure shows the cardinal and brachial processes of the dorsal 
valve*. 
Geological position and locality. In the shaly limestone of the Lower ILelderberg 
group : ILelderberg mountains, Albany county. 
* The letters of reference for the different figures of this and of the following species have been left out, 
through the inadvertence of the lithographer. 
