220 



teriorly. The lateral lobes have ten articulations, eight of 

 which are divided by a longitudiual furrow, the last two 

 are simple, and all become obsolete just within the margin. 



Surface of the head, except the anterior and lateral bor- 

 der, covered with small, somewhat pointed pustules, the 

 border having only a finely grannlose texture. Occipital 

 and axial ringsof the thorax and pygidium are each marked 

 with about seven small spiniform pustules, the central one 

 the longest ; those of the pygidium become closely crowded 

 in the posterior portion ; there are sometimes two or more 

 additional smaller pustules on the stronger lobes of the 

 thorax. 



Length of a medium sized specimen (exclusive of the 

 caudal spine) three inches; greatest width of the head 

 a little more than two inches; length of the head from the 

 occipital ring nineteen twentieths of an inch ; greatest 

 width of thorax one inch and nine tenths ; width of axial 

 lobe half an inch. Length of the pygidium (exclusive of 

 the spine) nine tenths of an inch ; greatest width of pygi- 

 dium one inch and nine twentieths. 



GENUS CYPHASPIS (Burm). 



Cyphaspis chpjstyi {Hall). 



General form of body elongate oval, the length nearly twice 

 the greatest width of the thorax. Head semioval, the pos- 

 terior margin slightly concave, highly elevated in the mid- 

 dle, bounded by a comparatively strong thickened rim ; 

 posterior angles prolonged into slender spines reaching to 

 the sixth or seventh thoracic segment, and slightly diver- 

 gent. Glabella small, broad ovate, rounded in front and 

 truncate behind, about half the length of the head ; great- 

 est width anterior to the middle, surface convex, very 

 prominent behind; some specimens show faint indications 

 of a pair of short oblique furrows anterior to the middle. 



