278 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



median line of the glabella ; they slope rather abruptly inward to 

 the nearly flat interpalpebral area. Visual surface of eye narrow 

 and arching around beneath the outer margin of the palpebral lobe. 

 Cheeks of medium wadth and sloping rapidly, with a gentle curva- 

 ture, from the base of the eye and the anterior glabellar lobe to the 

 intermarginal furrow ; a facial suture is indicated back of the eye 

 by a narrow ridge extending from the posterior end of the eye 

 obliquely outward and backward so as to cross the posterior mar- 

 ginal border obliquely about two-thirds of the distance from the 

 occipital ring to the genal angle. 



The portions of the thorax preserved show that the thoracic seg- 

 ments had a strongly arched axial lobe with a median spine on each 

 segment ; the pleural lobes are relatively short and of the same char- 

 acter as those of CaUavia crosbyi [pi. 28, fig. 4] ; the pleural furrow 

 is rather broad next to the axial lobe, from whence it narrows out 

 to the rather short falcate termination. The segments shown on the 

 specimen illustrated belong to the middle portion of the thorax ; 

 several of the other segments have been crowded up beneath the 

 cephalon, as shown by the breaking away of a portion of the cheek. 



Surface of the cephalon and of thoracic segments ornamented by 

 an extremely fine network of raised ridges, such as characterize the 

 surface of C. crosbyi [pi. 28, fig. 7]. There is also a series of very 

 fine irregular ridges radiating from the base of the eye and anterior 

 lobe of the glabella outward to the intermarginal furrow. 



Dimensions. — The type specimen of a cephalon has a length of 

 13 mm., with a width of 19 mm. The proportions of other parts of 

 the cephalon are illustrated by fig. 9, pi. 41, which is based on a 

 photograph enlarged two diameters. 



Observations. — This species is described from a single specimen 

 found in the conglomerate limestone at Bic. It shows an entire 

 cephalon and several of the middle segments of the thorax. The 

 illustration is drawn from a cast made in the natural matrix from 

 which the specimen was broken in breaking the limestone. Numer- 

 ous fragments of large thoracic segments similar to those of CaUavia 

 broggeri were found in the same' boulder of limestone, but there 

 were no traces of the cephalon except bits of the cheeks and palpebral 

 lobes. The ends of the pleur?e are illustrated by figs. 10 and loa, 

 pi. 41. 



CaUavia biccnsis dififers from C. crosbyi in the outline of the 

 cephalon and glabella, proportions of palpebral lobes, glabella, and 

 cheeks. It does not have the great occipital spine of C. broggeri or 

 the tapering, conical glabella of C. biirri [pi. 2^. fig. 9]. 



