336 
PALAEONTOLOGY OF NEW-YORK. 
Rhynchonella sulcoplicata (n. g.). 
Plate XXXY. Fig. 1 a, b, c. 
Shell subtriangular, wider than long, compressed. Yalves nearly equal : 
beak of the ventral valve prominent, attenuated, acutely pointed and 
arched : beak of the dorsal valve incurved. 
Surface marked by about sixteen simple longitudinally grooved plications, 
four of which are very faintly elevated towards the front of the dorsal 
valve, forming an indistinct mesial fold, corresponding to a sinus in the 
opposite valve which is occupied by three plications. 
A marked peculiarity of this species is the longitudinal groove along the centre 
of each of the plications. Of the four plications elevated on the dorsal valve, the 
two central ones are less prominent than the others, and separated by a deeper and 
wider depression which continues quite to the apex of the beak. 
Fig. 1 a , b. Ventral and front view. 
Fig. 1 c. Enlargement of the striae. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Albany county. 
Rhynchonella fonnosa (n. s.). 
Plate XXXV. Fig. 6 a - y. 
Shell subtriangular or transversely oval ; lateral margins forming an angle 
at the beak of about 90° to 110°. Ventral valve somewhat more depressed 
than the opposite : beak prominent, arched, not strongly incurved. 
Dorsal valve larger, declining with a gentle curve towards the margins : 
beak incurved. 
Surface marked by twenty to twenty-four simple angular plications on 
each valve, from two to four of which in the middle are coarser and 
depressed in the ventral valve, having a corresponding number abruptly 
elevated upon the dorsal valve; concentrically marked by line closely 
arranged striae. 
This handsome species may be recognized by the neatly rounded outline of the 
latero-basal margins, the abrupt sinus, and the stronger central plications. 
A single specimen from the same position as the above shows a less distinctly 
defined sinus and mesial elevation, with five plications on the latter and four in the 
former, and only six on each side. I am disposed to regard this as only a variety of 
the above, though future collections may prove it to be distinct. Fig. 2 a, &, c and 
