SHUMARD — NEW PALiEOZOIC FOSSILS. Ill 



posterior border nearer the genal angle than the dorsal fur- 

 row ; glabella ovate-conical, longer than wide, occupying 

 about two thirds the total length of the head, flattened con- 

 vex, front strongly and somewhat narrowly rounded, sides 

 contracted a little in advance of the middle and rounded be- 

 fore and behind the contraction ; no glabellar furrows ; occi- 

 pital furrow profoundly impressed and bifurcated near the 

 extremities, so as to leave a small, short, subtriangular lobe 

 between the branches ; occipital ring much wider than the 

 thoracic rings and less elevated than the glabella ; dorsal fur- 

 rows rather shallow but distinct ; eyes of medium size, not as 

 high as the glabella ; movable cheeks rather strongly convex 

 and bounded posteriorly by a deep furrow. 



Thorax slightly decreasing in width from the head poste- 

 riorly, composed often segments, trilobation strongly marked: 

 axis wider than the lateral lobes, subsemicylindrical, slightly 

 narrowing from before backwards, rings gently rounded and 

 separated by distinct narrow furrows ; lateral lobes flattened 

 the inner third of their width, and thence bending somewhat 

 abruptly downwards to the exterior margin. 



Pygidium nearly semicircular, depressed convex ; axal lobe 

 elevated, narrow conical, rounded at apex, not as wide as the 

 lateral lobes ; rings distinct but not prominent, separated by 

 shallow furrows ; lateral segments but little elevated, round- 

 ed, becoming obsolete before reaching the margin ; border 

 narrow and marked with a shallow depression all around. 

 The pygidium of the specimen is slightly abraded, so that I 

 can not count the rings and segments precisely, though their 

 number may be estimated at from nine to twelve. 



Length, 1.20 inches; width at base of head, 0.77 of an inch. 



This species appears to be somewhat nearly related to the 

 P. Haldemani (Hall) of the Hamilton Group of New-York 

 and Pennsylvania, from which it seems to differ by its greater 

 size, the absence of glabellar furrows, and other characters of 

 more or less importance. 



For the opportunity of describing this fine species I am in- 

 debted to the kindness of my friend, Dr. H. A. Prout of this 

 city, who found it, some years ago, a short distance above the 

 town of Davenport, Iowa, near the water-level of the Missis- 

 sippi, in compact gray limestone, supposed to be of the a«-e 

 of the Hamilton Group of the New-York series. 



It affords me much pleasure to dedicate this beautiful tri- 

 lobite to its discoverer. 



Genus El^acrinus, F. Roemer, 1852. 



There is, in my opinion, good grounds for separating from 

 the genus Pentremites those forms that have been hitherto 

 included in the group Elliptici of Prof. Roemer, and placing 



