36 ME. E. S. C0BB0LD OX THE TRILOBITE EAUXA [March 1913, 



posteriorly than anteriorly * ; the oval is surrounded by a convex 

 border, which expands at the sides into pointed and somewhat 

 flattened wings. The width across the points is nearly or quite as 

 great as the total length of the hypostoma. 



The border is traceable forwards as a narrow rim reaching the 

 anterior end, where it appears, from the specimens, to be bent 

 upwards at the margin. 



The postero-lateral angles are damaged in all the specimens : it 

 is, therefore, impossible to say whether they were furnished with 

 hooks. About half-way between these angles and the points of 

 the wings there is a little projection on each side. 



The convex body is covered with a close-set network of raised 

 lines, which are modified on the border and wings to linear 

 rugosities, parallel to the margins. 



No macular have been detected, nor any division of the convex 

 body, such as is shown and described by Walcott for Olenoides ellsi. 



Thorax (PI. Ill, figs. 10-12 & 15).— Only detached pleura?, and. 

 one complete but small thoracic segment, have been found. 



Axis. — Convex, probably spinose, or having a pointed node. 



Pleurae. — Short and wide ; abruptly bent downwards about half- 

 way out ; with a wide groove and strong anterior and posterior 

 ribs ; the anterior rib is prolonged to form a short rounded spine, 

 which is directed rather strongly backwards ; the posterior rib 

 curves forward at its termination to join the anterior at the base of 

 the spine. The spines of some pleurae (the anterior ?) are shorter 

 than those of others ; in front of the outer part of the anterior rib 

 there is a flattened shoulder-like expansion, or facet for enrolment. 



Pygiditjm: (PI. Ill, figs. 13-15). — The pygidia vary much in size, 

 one being but 2*5 millimetres long, others measure 4 to 5 mm., 

 and yet other fragments indicate a length of 16 mm. 



General form. — Approaching a semicircle; convex: the con- 

 vexity ratio of one small specimen being about 1 : 4. 



Axial lobe. — Yery convex; about a third of the total width of 

 the shield anteriorly, but tapering backwards to the rounded ex- 

 tremity ; reaching to the inner margin of the border ; divided by 

 six 2 grooves into — the anterior articulating facet, four subequal 

 divisions, one shorter division, and the somewhat bulbous and 

 rather longer terminal division ; the last groove is much less 

 distinct than the others ; the descent to the border is but mode- 

 rately steep ; there are no spines or nodes on any of the divisions. 



Lateral lobes. — Sub-triangular; moderately convex; marked 

 by four distinct furrows, with intermediate flattened ribs between 

 them ; sometimes there are traces of fifth and sixth farrows pos- 

 terior to these : the anterior rib is narrow and well rounded, and 

 is traceable across the border. 



Border. — Continuous round the sides and end of the pygidium ; 



i The terms anterior and posterior are used here in accordance with 

 the actual position of the plate when attached to the head-shield. 



2 In the restoration (PI. Ill, fig. 13) one of these grooves has been omitted. 



