268 PROCEEDINGS OF THE ACADEMY OP 



narrow on their upper edges, flattened in the direction of the axis, and bent 

 a little backwards below the knees, apparently rounded at the extremities. 



Pygidium subsemicircular, but 3 little rounded at the anterior lateral 

 angles ; about one-third wider than long, and as long as the glabella, exclu- 

 sive of the neck segment and anterior marginal rim ; rather more broadly 

 rounded behind than the anterior margin of the glabella ; mesial lobe promi- 

 nent, about as wide anteriorly as the lateral lobes, and tapering backwards to 

 an obtuse point within the margin, where it ends rather abruptly and is a 

 little depressed, but not flattened ; consisting of nine or ten moderately de- 

 fined segments ; lateral lobes depressed below the mesial lobe, near which they 

 are slightly flattened, thence rounding to the margins ; each with about seven 

 rather faintly defined segment*, of which only the anterior one is marked with 

 a longitudinal furrow, all extending to within a short distance of the margin, 

 which seems to be slightly thickened. 



Surface apparently nearly smooth excepting the glabella, which is covered 

 with small, rather closely arranged granules. A row of very small granules 

 may also be seen, by the aid of a magnifier, along the posterior margin of the 

 segments of the mesial lobe, both of the thorax and pygidium. 



Entire length", 0-78 inch ; do. of pygidium, 0-23 inch ; do. of thorax, - 25 

 inch; do. of head, O30 jnch. Breadth of head, 0'39 inch; do. of thorax, 

 <V3b' inch; do. of pygidium, - 34 inch. Length of glabella, including neck 

 segment, 0-25 inch, exclusive of neck segment, 021 inch ; length of eyes, 

 O'lO inch; distance of same in advance of posterior margin of cheeks, 0"06 

 inch. 



At a first glance this species might be readily mistaken for P. Swallowi, of 

 Dr. Shumard, from the same horizon. A moie careful comparison, however, 

 at once shows it to present well defined specific differences. In the first place, 

 the outline of the anterior margin of its head is more regularly rounded, its 

 entire cephalic shield longer in proportion to its breadth, while its postero- 

 lateral angles are produced into small spines. Its glabella also differs in being 

 a little narrower anteriorly than behind, instead of the reverse, and its sides 

 straight instead of sinuous. The posterior lateral lobe of its glabella likewise 

 differs in being entirely isolated by the furrow ju-t in advance of it intersect- 

 ing the neck furrow, and the other lateral furrows are less distinct than in 

 P. Swalloiri. Again, our species differs in having its glabella granulose, and 

 the segments of its medial lobe each provided with a row of minute marginal 

 granules, instead of having " the whole surface minutely punctate." 



It is very probable we should call this species Phillijisia dhptica, as it seems 

 to present most of the characters of that genus. Unfortunately, the charac- 

 ters distinguishing these groups seem not to have been very clearly pointed 

 out. 



Locality and position. Jersey County, Illinois. Kinderhook Group, of 

 Subcarbonit'eious series. 



Genus PHILLIPSIA, Portlock, 1843. 



Subgenus GRIFFITHIDES, Portlock, 1843. 



Phillipsia (Gkiffithides) Portlockii, M. & W. 



Entire outline subovate. Cephalic shield subsemicircular, nearly twice as 

 wide as long, moderately convex, rounded in front and straight behind, with 

 the posterior lateral angles terminating in short, pointed, spine-like appenda- 

 ges extending back to the third thoracic segment. Glabella ovate, tumid, con- 

 tracted and depressed behind, widest and most convex anteriorly, where it is 

 about one-thiid narrower than its length from the neck segment to its rounded 

 front, which is not margined by a projecting rim; very distinct from the 

 cheeks in consequence of its greater convexity ; posterior lateral lobes small, 

 much depressed, and isolated by the oblique lateral furrows in front being so 



[Dec. 



