Monograph of the Crustacea of the Cincinnati Group. ' 145 



Eyes comparatively large and prominent, separated from the glabella 

 by a somewhat deep groove ; border of the head broad and flattened. 



Thorax having the axial lobe very prominent, narrower than the 

 lateral lobes ; segments scarcely arching forward in the middle ; lateral 

 lobes geniculate, and having the extremities of the pleura directed 

 backward and distinctly furrowed to near their outer extremities. 



Pygidium small, semi-circular, regularly rounded behind, and the 

 anterior margin straight to near the lateral angles, where it is abruptly 

 curved backward. Axial lobes narrow, not reaching to the posterior 

 border of the shield ; marked by five small annulations, with about 

 the same number on the lateral lobes, which are less distinctly marked. 

 Surface smooth or very finely granulose. 



This species has been found at Cincinnati, but only two specimens 

 that I am aware of. They were both found near the top of Vine street 

 hill. 



Prcetus Simrhcki— (Meek, 1872). 



General form, exclusive of the spines of the cephalic shield, ovate 

 sub-elliptic, with moderate convexity. Cephalic shield having the 

 form of one of the halves of an ellipse divided through its shorter 

 diameter, its posterior margin being straight, and its anterior narrowly 

 rounded ; posterior lateral angles produced into long, sharp spines, that 

 extend back nearly or quite the entire length of the thorax ; glabella 

 nearly one third the breadth of the posterior part of the head, sepa- 

 rated from the cheeks on each side by a well defined furrow, but with- 

 out having the neck furrow distinctly marked ; other details of glabella 

 unknown. Eyes sublunate, nearly their own length in advance of the 

 posterior margins of the cheeks. 



Thorax- having eight segments. Mesial lobe moderately prominent, 

 scarcely equaling the breadth of the lateral lobes anteriorly, and taper- 

 ing more rapidly backward, with its segments not arching forward. 

 Lateral lobes less convex than the middle one ; pleurre nearly straight 

 and transverse, or very slightly curved backward, and furrowed for a 

 little more than half way out with their extremities rounded in front? 

 and nearly rectangular behind. 



Pygidium sub-semi-circular, about one half as long as the cephalic 

 shield, and provided with a smooth, flattened margin. Mesial lobe 

 moderately prominent, narrower than the lateral; tapering posteriorly, 

 where it terminates rather abruptly, without passing quite upon the 

 flattened margin, showing only very obscure traces of five or six seg- 

 ments on its anterior half. Lateral lobes more depressed than the 



