104 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



The border is wide, but the details cannot be made out. The posterior an- 

 gles are produced in spines, which reach as far as the fourth (and perhaps 

 the fifth) articulation of the thorax. 



The thorax has the middle lobe very large and extremely convex, its 

 width in the middle being greater than the width of the lateral lobe ; gra- 

 dually tapering from the anterior, and almost pointed at the posterior ex- 

 tremity in the pygidium : dorsal furrow strongly marked, with a slight 

 depression of the lateral lobes towards the furrow, thence a little flattened 

 and regularly curving downwards to the margin. 



The pygidium is very convex, twice as wide as long and nearly semicircu- 

 lar, being a little narrowed below the middle ; the axis prominent, conical, 

 marked by ten or twelve* rings, which are vertical or ascending near the 

 base, and a little bent backwards near the top and sides : lateral lobes 

 marked by seven or eight ribs, some of which are marked by a longitudinal 

 groove a little above the centre. Surface granulose. 



This species is readily distinguished by the ovate form, great convexity, 

 prominent glabella and robust axis, which, from being wider than the lateral 

 lobes at its anterior extremity, tapers nearly to a point in the pygidium. 



Geological formation and locality. In the coarse sandy shales of the 

 Hamilton group : at Fly creek and other places in Otsego county ; and in 

 the coarser shales and conglomerate beds of the same group in Schoharie 

 county, N.Y. 



PROETUS MARGINALIS. 



Calymene marginalis [? ] : Conrad, Ann. Rep. Palaeontology N.York, 1839, p. 66. 



" C. MARGINALIS. Bucklcr with a broad margin : eyes large, semi- 

 " oval; middle lobe entire, convex, smooth; abdomen " 



^^ Locality, near Ithaca, in a boulder. This has a much less prominent 

 " front than the [ C] rowi, a deeper groove between the eye and middle 

 " lobe ; and the tubercle, which nearly joins the lower angle of the eye, is 

 " much smaller." 



The boulder alluded to is a large mass of the TuUy limestone many miles 

 south of the outcrop of that rock ; and from this circumstance, I am induced 

 to regard the Proetus of this rock as the fossil described by Mr. Conrad. 



The entire form of the body is oval-ovate ; the length about once and a 

 half as great as the width. The head is margined by a wide border, which 

 is produced into short posterior spines. The groove in front of the eye is 

 narrow and well defined, becoming broader on the cheeks. Beyond the groove 

 the border is at first convex, thence sloping abruptly and spreading in a 



* Ten can be counted, and there is space for two more; but I have no specimen 

 which clearly shows the full number 



[ September, 



