108 PALAEONTOLOGY OF OHIO. 



" The pygidium is gibbous, semi-elliptical, with the axis very prom- 

 inent, and marked by seven rings, the last one being longer and more 

 prominent, with a minute, scarcely defined node at the extremity ; lat- 

 eral lobes marked by six flattened ribs, the last one of which is minute, 

 the expansion being continued in a narrow, flattened border around the 

 posterior extremity." 



The above is a copy of the original description of the species. There 

 may be some doubt in regard to the correct reference of this species to 

 the genus Calymene, as many of its features would seem to ally it as 

 closely to the genus Homalonotus. M. Barrande, in his great work on 

 the trilobites of Bohemia, refers to that genus a species (H. Bohemicus) 

 which bears a striking resemblance to this one. The facial suture, upon 

 which considerable reliance is placed, has the character of the latter 

 genus, rather than of that of Calymene, passing, as it does, around the 

 front of the glabella, on the upper side of the head, instead of below. 

 The form of the glabella is intermediate between that of the two genera, 

 but most like that of Homalonotus, although there is evidence of three 

 pairs of furrows in this species. The thoracic segments are very similar 

 to Homalonotus, while the pygidium resembles more nearly that of Caly- 

 mene. There is no described American form of either genera with which 

 this species is readily confounded, as the general expression of the whole 

 body is so distinct from any known species. The short spines at the pos- 

 terior angle of the fixed cheeks is a feature often seen on well preserved 

 specimens of Calymene senaria, as it occurs in the formations in the 

 vicinity of Cincinnati, Ohio. 



Formation and locality: In the Hudson River group, near Oxford, Ohio; and, so 

 far as we are aware, it has not been found at any other locality. 



Genus DALMANIA, Emerich. 

 Dalmania breviceps. 



Plate 4, figs. 16, 17. 



Dalmania breviceps, Hall ; Extr. 20th Rept. State Cab., p. 16, rSQQ ; 24th Kept. State Cab., 

 p. 223, pi. 8, figs. 15 and 16. 



The following description is that originally given, as above cited : 



" Body broadly ovate in general form, having its greatest width across 



the base of the cephalic shield. Head sub-crescentiform, the anterior 



margin very slightly produced in front of the glabella. Frontal lobe of 



glabella transversely elliptical, the breadth nearly twice as great as the 



