ORISKANY SANESTONE. 
443 
Ithyiichonclla principalis. 
Plate CYI. Fig. 4. 
Rhynclionella principalis : Hall, Regents’ Report for 1856, p. 84; Palaeozoic Fossils, 1857, p. 44. 
Shell longitudinally ovate. Dorsal valve unknown. Ventral valve de¬ 
pressed convex, forming a low elliptical arch from beak to front, most 
prominent along the middle, flattened or somewhat concave near the 
lateral margins, which are abruptly inflected towards the opposite valve : 
beak somewhat prominent, and moderately incurved; front slightly 
concave, but not distinctly sinuate. 
Surface ornamented by about eighty regular rounded plica,tions, which 
occasionally bifurcate, and are crossed by indistinct lines of growth. 
This species is closely related to R. barrandi ; and having but a single ventral 
valve, I cannot readily decide how far it may differ in its entire characters. The 
casts of the preceding species are all proportionally broader when not compressed* 
have a more distinct sinus in front, and fewer plications. With the knowledge at 
present possessed, this species may be considered as holding a place intermediate to 
the very well marked R■ speciosa and the equally well marked R. barrandi. 
Fig. 4. View of the ventral valve, natural size. 
Geological position and locality. In the Oriskany sandstone : Auburn, Cayuga 
county. From Professor Hopkins. 
f 
lihyiiclionella septata (n. s.). 
Plate CIII. Fla. 2. 
The specimen is a cast of the dorsal valve, which shows, near its margin, in¬ 
distinct marks of a few plications, with the impression of a median septum reaching 
nearly to the base, which has been extremely thickened towards the beak. The 
crural processes have been very large and strong, and projecting above these was a 
strong bilobed process. 
Geological position and locality. In the Oriskany sandstone : Albany county. 
