134 PALEONTOLOGY OF NEW YORK. 



which arc well developed in this species, are either obsolete or obsolescent in 

 Phillipsia. The ten thoracic segments, however, determine its generic relations 

 and exclude ii 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. 



Pleura 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 

 Vha< thonides gemmtzus, 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. 



