528 GEOLOGY OF OHIO. 



the posterior margin of the same, curving regularly inwards and back- 

 wards, forming large round posterior lobes, similar to those of Sphczrex- 

 ockus, the defining groove terminating abruptly before reaching the 

 nuchal furrow. A little anterior to the middle of the glabella lies the 

 middle, much shorter pair of furrows, also curving more or less back- 

 wards. A third, very short pair, lies still farther forward. A strong nar- 

 row furrow defines the glabella anteriorly, in front of which lies the very 

 narrow margin of the head, only wide enough to receive an irregular 

 row of granules, of about the same size as those ornamenting the entire 

 glabella. The granules of the glabella vary greatly in size, smaller ones 

 being interspersed among those of larger size, the general effect being 

 decidedly granular as in species of Lichas. 



Sphcerexochus pisum, sp. nov. 



'Plate 37A, Figs. 14, a. b. 



In the Niagara shales at Lockport, New York, are found small glabeh 

 lae presenting from above and in front a decidedly globular aspect. An- 

 terior to this globose glabella is a deep, very distinct groove, separating 

 as far as known only a very narrow border or rim, forming the anterior 

 margin of the head. Laterally this groove curves around strongly, then 

 upward and backwards, until, after a strongly concave curvature along 

 the side of the glabella, separating, it is presumed, the fixed cheeks, it 

 connects with the strongly characterized occipital groove. The occipital 

 segment is strongly arched from side to side. No evidence of segmenta- 

 tion or furrows occur on the glabella. The surface of the glabella is 

 ornamented by distinct larger granules, between which are interspersed 

 much smaller ones. Both are best developed towards the circumference 

 of the glabella, the larger granules becoming less distinct and widely 

 separated towards the centre of the glabella, while the smaller granules, 

 though becoming much more frequent near the centre, are smaller and 

 far less distinct over the central regions of the glabella. In a figurative 

 sense they may be said to have a somewhat "bald headed" appearance. 

 The type specimen is 5 mm. long and antero-posteriorly the outline of 

 the head describes slightly 'more than a semicircle. (Plate 37 A, Figs. 14, 

 a. b.) Obtained in exchange from the cabinet of Dr. E. N. S. Ringue- 

 berg. 



In the limestones of the Clinton Group at Soldiers' Home two speci- 

 mens of this species were found which are evidently the Clinton progenitors. 

 One of these was an imperfect fragment of the glabella. The other, 

 collected by Mr. Geo. Caswell, presented almost the same characteristics 

 as the New York Niagara type. The chief difference consists in a 

 slightly less globose curvature, and in the greater coarseness of the or- 

 namentation, there not being such a fine distinction between the large 



