NATURAL SCIENCES OF PHILADELPHIA. 271 



distinctly kneed near the middle, outside of which they are bent down and 

 obliqely flattened for folding together and rounded at the extremities. 



Pygidium very convex, smaller than the cephalic shield, forming more than 

 a semicircle, with the anterior lateral angles obliquely truncated ; posterior 

 outline regularly rounded, with a moderately wide, smooth, depressed, nearly 

 fiat, or sloping marginal zone ; trilobation, as in the thorax, strongly defined ; 

 mesial lobe prominentias wide anteriorly as one of the lateral lobes including 

 its border, distinctly flattened on each side, slightly tapering to an obtuse ter- 

 mination, less than half its own greatest anterior breadth from the posterior 

 edge, segments eleven or twelve, well defined above, but nearly obsolete on 

 the flattened sides. Lateral lobes convex, but distinctly less so than the mesial 

 lobe, horizontally flattened near the latter, with an angle along the outer 

 margin of the flattened space, from which the sides slope abruptly to th 

 flattened, smooth border ; segments six, simple, bent down in the middle, 

 very distinct, but terminating abruptly at the rather wide border ; each with 

 a minute pustule on the knee. 



Surface of glabella and all the segments more or less granulose, the gran- 

 ules being larger on the posterior part of the glabella and neck segment than 

 elsewhere. 



Entire length, 0*60 inch. Length of pygidium, 0*19 inch ; breadth of do. 

 0*27 inch ; length of thorax, 0*18 inch ; breadth of do. 0*28 inch ; length of 

 cephalic shield, 0-23 inch ; breadth of do. 0-32 inch. 



As near as can be determined by a description of the pygidium alone, thia 

 species would seem to be nearly related to P. Cliftonensis, of Shumard. The 

 middle lobe of its pygidium, however, is proportionally wider than in that 

 speeies, being as wide as one of the lateral lobes including the smooth border ; 

 while in P. Cliftonensis it is said to equal one of the lateral lobes exclusive of 

 its border ; in addition to this, Dr. S. makes no allusion to the flattened sides 

 of this lobe, so characteristic of our species. We do not believe it always 

 possible, however, to distinguish allied species of this genus from the pygidia 

 alone, and hence, think it would be better if Palaeontologists would never pro- 

 pose a species without seeing also some of the other parts. At the same time 

 that our species may be identical with that described by Dr. S., it is far more 

 probable that if we could compare entire specimens of each, we would find 

 them entirely distinct. 



We know of no described species, the head of which could be confounded 

 with this ; its comparatively large convex eyes, and distinct mesial node be- 

 ^veen the posterior lateral lobes of the glabella, and the deep vertically flat- 

 tened and striated lateral margins of its cheeks are marked characters, that 

 will readily distinguish it. Whether the proposed genus Griffithides is to be 

 retained as a genus or a subgenus, this must be included in it, since it has the 

 posteriorly contracted glabella and. smooth eyes of that type. We do not be- 

 lieve, however, that non-reticulated eyes in any type of Trilobites proves 

 them to have been blind, for as in this case, they were doubtless always 

 provided with minute lenses beneath a transparent outer crust. 

 Locality and position. Upper Coal Measures, Springfield, Illinois. 



Phillipsia (Geiffithides ?) Sangamonejjsis, M. & W. 



Entire outline elongate subovate. Cephalic shield very convex, forming 

 more than a semicircle, and about one-third wider than long ; regularly 

 rounded in front and straight behind, with posterior lateral angles produced 

 into rather broad, carinated, pointed or subspinous appendages, equalling in 

 length the distance from the posterior side of the cheeks to the anterior end 

 of the eyes. Glabella ventricose, very prominent, separated from the cheeks 

 on each side by a moderately distinct furrow, which also passes around the 

 front ; most convex behind the middle, thence rounding and declining to the 

 rounded front, about one-fourth longer than wide, and slightly wider between 



1865.] 



