78 CARBONIFEROUS TRILOBITES. 



Two other Canadian species of uncertain horizon complete the list : 



Phillipsia Howi, Billings, 1863. 



„ Vindobonensis, Hartt, 1868. 



On both sides of the Atlantic, therefore, so.far as I am aware, the Carboniferous 

 Trilobites without exception belong to the type possessing a pygidium with definite, 

 even outline, like that of the two genera given above. It is true, Meek says, in 

 his description of Phillipsia Lodiensis ('Pal. of Ohio,' vol. ii, p. 324), "The 

 fimbriated character of the posterior and lateral margins of the pygidium is very 

 peculiar and hitherto unknown, I believe, in either of the above-mentioned genera " 

 (Phillipsia and Griffithides), " though it occurs in one section (Phaethon) of the 

 allied genus Proetus ; hence, it is possible that our species should be called Proetus 

 (Phaethon) Lodiensis, as it would not be very surprising that this genus should be 

 found in this oldest member of the Carboniferous, though hitherto, I believe, only 

 known in the Silurian and Devonian." l 



The crenate character of the margin of the pygidium here alluded to must 

 have been exceedingly slight in the typical specimen, as not a trace of it appears 

 in the figure (pi. xviii, fig. 3). Prof. Meek says of this feature, " The segments 

 are continued down upon and across the sloping border, at the edge of which they 

 terminate in little pointed projections so as to present a fimbriated appearance 

 around the posterior and lateral margins. (This latter character is not represented 

 in the figure.)" 



It is obvious from the terms here employed that the crenation alluded to in no 

 wise resembles the pointed and almost spinous margin of the species described 

 below. I may add that specimens of Phillipsia Lodiensis from the Cuyahoga 

 shale of this county (Summit), only a few miles from the locality of Prof. Meek's 

 type, show no perceptible crenation. 



In regard to the two species of Proetus on the list given above, P. ellipticus and 

 P. auriculatus, a few words may be added. I have not seen specimens of either, 

 but the description of the former by its authors shows that it differs very slightly, 

 almost imperceptibly, from Phillipsia. They remark in conclusion, " It is very 

 probable that we should call this species Phillipsia elliptica, as it seems to present 

 most of the characters of that genus. Unfortunately, the characters distinguishing 

 these groups seem not to have been very clearly pointed out." (' Proc. Acad. Nat. 

 Sci. Phil.', 1865, p. 267-8.) 



The pygidium of Proetus auriculatus, Hall, is not certainly known. That 

 which is supposed to belong to this species is " marked by seven or eight ribs 



2 In writing this sentence, 1875, Prof. Meek seems to have forgotten his own Proetus ellipticus of 

 1865, and Prof. Hall's Proetus auriculatus of 1861, the former from the Kinderhook, and the latter 

 from the Waverley Sandstone. 



i 



