Monograph of the Crustacea of the Cincinnati Group. 133 



at the base, and the posterior angles extended into long curved spines ; 

 eyes small, distant, sublunate, granulated (not reticulated) ; glabella 

 clavate, more or less convex, deeply four lobed on each side, leaving 

 the front one broader ; thorax with eleven articulations ; pygidium 

 with four (scarcely five) anchylosed articulations in the axial lobe, 

 and three on each lateral lobe, the upper of these lateral articulations 

 thickened and extended into a long, curved spine, the others terminat- 

 ing in blunt points ; surface entirely papillose or granulated, the ce- 

 phalic shield with scattered larger tubercles ; two ranges of sinall papil- 

 lose tubercles along the center lobe, and three ranges of mammillary 

 tubercles on each lateral lobe ; labrum sub-trigonal in outline, convex 

 in the middle, and granulous over the surface. A depression near the 

 margin of two sides forms a marginal rim, from the terminations of 

 which it attaches to the cephalic shield. 



The whole surface, when perfect, is papillose. Upon all parts of 

 the cephalic shield are interspersed small mamillary tubercles, and two 

 similar ones on each articulation of the axial lobe, making two ranges 

 of tubercles. Each articulation of the lateral lobes presents three 

 large mammillary tubercles ; the first formed by an oblique furrow 

 from the upper side of the articulation, downward and outward ; the 

 third by a furrow from the upper edge downward and inward, or 

 toward the axis ; the meeting of these furrows leaves above them the 

 second or middle tubercle. 



A good specimen of this species is extremely rare, and even frag- 

 ments are by no means abundant in any known locality. It is found 

 at the quarries back of Cincinnati, at all elevations, from 300 to 450 

 feet above low water-mark. Probably the labrum is found the most 

 frequently of any fragment of it. 



Ceraiinis icarus — (Billikgs, 1859). 



General outline ovate sub-elliptic, moderately convex. Cejjhalic 

 shield nearly semi-circular, rather more than twice as wide as long, 

 regularly rounded anteriorly, and nearly straight behind, excepting 

 near the lateral angles, where it curves somewhat abruptly backward, 

 on each side, into the lateral spines, Avhich are small, and scarcely ex- 

 tend farther back than to the second thoracic segment. Glabella, ex- 

 clusive of the neck segment, about as wide as long, with its lateral 

 margins so nearly straight and parallel as to make its breadth almo.-^t as 

 great anteriorly as behind ; separated from the cheeks by narrow but 

 well defined furrows, that unite around the front, so as to leave a very 

 nari'ow border between its anterior margin and that of the cephalic 



