F. R. Cou-pcr llecd — Unde-'^cribed Trilohitcs. 1 -li- 



the anterior part of the pleura is flattened into an articulating surface 

 which passes underneath the preceding pleura. Fulcrum well- 

 marked and angular, at the junction of the inner and outer portions 

 of the pleura. Extremities of pleuras truncated and rounded. 



Pygidium semicircular, about two-thirds the length of the thorax ; 

 with simple entire margin, and distinct raised border. The anterior 

 edge of pygidium resembles that of a pleural ring, the inner part 

 being short and straight and the outer part oblique with an 

 articulating surface. Lateral and posterior margins incurved and 

 concentrically striated below. 



Axis conical, strongly elevated above the flattened lateral lobes, 

 and tapering more rapidly than axis of thorax to an obtusely pointed 

 extremity, reaching the marginal furrow inside the raised boi'der. 

 Seven to eight rings recognizable on axis, of which only the three 

 first are clearly separated by strong intersegmental furrows, the 

 posterior ones being more or less indistinct. Lateral lobes gently 

 bent down on each side, and marked with three or four pleune 

 with inner horizontal portion generally distinguishable, but devoid 

 of fulcrum. A weak longitudinal furrow runs down the centre of 

 each pleura. 



Border of pygidium distinct and raised slightly above level of 

 lateral lobes, narrower at anterior lateral angles and behind axis 

 than in middle of sides. It is marked off by a shallow marginal 

 groove, and in one specimen {a 825 of Salter's Catalogue) the 

 pleuras and their furrows are faintl}' traceable across it, but in some 

 individuals it is vei'y indistinct. 



Ornamentation. — The whole surface of the head and pj'gidinm is 

 finely granulated. 



Measure3ients. — Salter's specimen a 82o : — 



luiu. 



Length of whole trilohite 22-(» 



Length of head-shiekl ... ... ... ... 8-0 



Length of thorax 8-0 



Length of pygiihuni ... ... ... ... 6*0 



Wkitli of head-shiekl at hase lo-o 



Width of pygidium ... ... ... ... lO'o 



Width of glahella at base 6-0 



Eemarks. — This species resembles Pr. holiemicus, Corda,^ in the 

 following particulars : (1) shape, relative size, and proportions of 

 glabella; (2) presence of lateral nodules and median tubercle on 

 occipital ring ; (3) relative proportions of thoracic axis and pleura- ; 

 (4) characters of pleura? ; (5) shape of pygidium, pygidial axis, and 

 border; (6) granulated test. 



Pr. hoJtemicns diflfers, however, in having a semicircular rather 

 than parabolic head-shield, in possessing very short genal spines, 

 smaller eyes and eye-lobes, and a relatively narrower border to the 

 head-shield ; in the presence of three pairs of lateral furrows on the 

 glabella ; in the greater length of the thorax ; and in the smaller size 



1 Coi-da: I'ri.dr. Eulun. Trihib. (1S47), p. 73, ])1. iv, fig. 4:'.. Banaude : Syst. 

 Sihir. Bohem., v..l. i (1852), p. 452, pi. xvi, ligs. l-l--). 



