222 



GENUS LICHAS (Dalman). 



LlCHAS BREVICEPS {Hall.) 



Head broad and short, somewhat crescentiform, protruding 

 in front and prominent in the middle, the length about 

 one third as great as the width, posterior angles directed 

 backwards in short obtuse spines. Glabella very convex, 

 wider than long, rounded in front, distinctly divided into 

 three lobes, two lateral and one central, the central lobe 

 narrow behind and rapidly expanding in front, the lateral 

 lobes reniform and about as wide as the posterior part of 

 the central or anterior lobe, commencing forward of the 

 eye and reaching to the occipital furrow. Eyes very promi- 

 nent, reniform, very convex on the visual surface (having 

 the appearance of the eyes in Illa?nus). Anterior border of 

 the head very narrow in front of the glabella, being only 

 a rounded rim. Cheeks flat or slightly concave, with a 

 prominent rounded ridge just beneath the eye. Occipital 

 ring prominent ; furrow deep, becoming very faint in its 

 extension into the cheek furrows. Surface of the head 

 marked by very fine scabrous pustules. 



A pygidium found associated with the head above de- 

 scribed, presents the following characters. General form 

 nearly semicircular, a little rounded on the anterior bor- 

 der. Axial lobe broad and strong, very prominent in the 

 anterior part, rapidly narrowing, and becoming low in the 

 middle, and again widening posteriorly; its width at the 

 anterior margin being about one third as great as the whole 

 width of the tail ; annulations scarcely or faintly marked. 

 Lateral lobes with three segments each, and each marked 

 by a broad, shallow longitudinal furrow ; at ^the posterior 

 side of the two anterior ones the margin of the shield is 

 slightly notched, below this it is entire. The two an- 

 terior segments are curved a little backwards, while the 

 third one is curved first outwards and then downwards. 



