134 
PALEONTOLOGY OF NEW YORK. 
which are well developed in this species, are either obsolete or obsolescent in 
Phillipsia. The ten thoracic segments, however, determine its generic relations 
and exclude it from the genus Phillipsia, while the relatively short pygidium is 
more strongly Proetoid than Phillipsioid. 
PHAETHONIDES, Angelin. 1878. 
Phaethonides arenicolus, n. sp. 
PLATE XXV, FIGS. 12,13. 
Pygidium relatively short, broadly sub-elliptical in outline; length equal to one- 
half the width. 
Axis elevated, comparatively narrow, having less than one-third the width 
of the shield on the anterior margin; tapering to a blunt extremity consid¬ 
erably within the margin. Characterized by transverse annulations, the 
number of which cannot be distinctly made out, apparently from five to seven. 
PleurcB broad, curving rapidly to the margins; bearing five annulations, 
with traces of a sixth, all of which are strongly sulcate, the posterior limb 
being much the wider, and the anterior ridge becoming extinct upon the 
lateral slope. Each annulation terminates upon the margin in a short, stout 
spinule, projecting horizontally, and the post-axial margin also bears two of 
these processes, making in all fourteen in the marginal fimbria. Close upon 
the margins of the lateral slopes are also bases of spinules equally stout, and 
there appears to have been a row of small tubercles further inward on the 
posterior limb of each annulation. 
This pygidium appears to be constructed on the same plan as that of 
Phaethonides gemmceus, of the Hamilton group, but the number of annulations 
is somewhat less, and the surface not so strongly tubercled. 
The single specimen from the Schoharie grit has a length of 3 mm., and a 
width of 6 mm. 
Distribution. Upper Helderberg group. Schoharie grit: Schoharie county. 
A specimen bearing similar characters has also been found in the decomposed 
Corniferous chert at North Cayuga, Province of Ontario. 
