108 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



PROETUS OCCIDENS (n.s.). 



The pygidium is semielliptical, having a length of three-fourths of 

 an inch by a width of nearly one inch ; the axis of moderate 

 elevation, rounded and tapering to a narrow extremity, marked 

 by ten or more rings : dorsal furrow not strongly defined; the 

 lateral lobes sloping gently from the furrow for two-thirds their 

 width, and beyond this more abruptly ; marked by nine or ten 

 flattened ribs, beyond which the markings are obscure. 



Surface finely granulose. 



This species, in proportions of the pygidium, resembles some of the flat- 

 tened specimens of P. macrocephalus ; but the rings of the axis and ribs 

 of the lateral lobes are fewer, and are not pustulose. It is very distinct from 

 any species described in this paper. 



Geological formation and locality. In the shaly limestone of the age of 

 the Hamilton group : at New-Buffalo, Iowa. 



n.s.). /^I'/'^ 



PROETUS LONGICAUDUS (n.s.). ' ^' f / ' J 

 Entire body elongate-ovate, gradually tapering in a curved line to 

 the posterijOr extremity. Head broadly semielliptical, very convex 

 in the transverse direction ; the limb wide and thick, gently 

 depressed in front of the glabella, and sloping to the margin; 

 posteriorly the border has been produced into angular or spini- 

 form extensions. The glabella is ovate, slightly contracted and 

 nearly straight for a little distance in advance of the eyes, and 

 then abruptly rounded in front; extremely convex between the 

 eyes, and somewhat abruptly sloping towards the front. The 

 anterior furrow curves gently from the anterior angle of the 

 palpebral lobe, and reaches halfway to the centre of the glabella: 

 the middle furrow rises from nearly opposite the anterior fourth 

 of the eye, and is a little longer than the anterior furrow; the 

 posterior furrow rises from opposite the middle of the eye, and 

 curves gently backwards, coming out on the base of the glabella 

 so that the tw^o divide its width into three nearly equal parts. The 

 occipital furrow is narrow and sharply defined; the occipital ring 

 a little stronger than the body rings, and flattened at the dorsal 

 furrow, but without nodes. Eyes neatly defined, prominent and 

 semioval. 

 The thorax is short, with parallel, sides and a prominent semi- 



[ September, 



