136 
PALEONTOLOGY OF NEW YORK. 
Dimensions. An average cephalon measures 6 mm. in length and 6 mm. 
in width; the pygidium 8 mm. in length and 10 mm. in width. 
Observations. In the outline and contour of the cephalon, Pha'ethonides vari¬ 
cella apj)roaches Cyphaspis ornata, of the Hamilton group. Its more elevated 
and sharply recurved frontal margin, and the absence of the peculiar marginal 
ornamentation of that species, will serve as distinguishing characters of the 
head. The species is thus far represented by three specimens, two imperfect 
cephala and a single pygidium. Of these, one head and the pygidium occur in 
juxtaposition, so that little doubt remains of their specific identity. 
Distribution. Upper Helderberg group. Corniferous limestone; In the 
boulders of decomposed chert, Canandaigua, Ontario county. 
Phaethonides GEMMiEUS, n. sp. 
PLATE XXIV, FIGS. 32-36. 
Cephalon unknown. Two detached thoraces have been found, one in close 
association with a pygidium, and each of them shows seven segments. It is, 
however, probable that some of the segments have been lost. 
Thorax sub-quadrate, margins nearly parallel. 
Axis strongly arched and very broad, being nearly one-half the width of 
the body on the anterior margin; width increasing backward for a short 
distance and thence tapering rapidly toward the pygidium. Each segment 
is very narrow, elevated upon the anterior margin, grooved and depressed 
behind. 
Pleura, convex for about one-third their width, thence abruptly depressed 
to the margins; sulcate and strongly beveled for two-thirds their length. 
The axis bears from three to five longitudinal rows of small pustules, one 
of which is in the axial line, and the pleurae bear each three or four similar 
rows. The articulating grooves of the axis are punctate. 
- Pygidium. Outline sub-semicircular, anterior margin curved backward at the 
antero-lateral angles. Surface sharply elevated along the median line, de¬ 
pressed-convex on the lateral portions. 
