498 SILURIAN TRILOBITES, 



Sp. Char. — Body— Ohlon^ oval. Head-shield or cephalon. — 

 Subsemicircular, width rather greater than twice its length. 

 Glabella, including the neck ring, about five-sixths of the greatest 

 width, very slightly convex above, slightly subpentagonal, over- 

 hanging very little in front, sides straight and steep, limb very 

 rudimentary, and the furrow between it and the glabella faint ; 

 three pairs of lateral grooves present, frontal pair passing out 

 at the front angles and running obliquely across the glabella, 

 terminating subfalcately ; second pair opposite posterior horns 

 of eyes, both of these pairs are linear; intercalary groove 

 moderately distinct, wide and shallow ; intercalary ring with 

 well-marked nodules at each end; the whole glabella surface 

 ornamented with various-sized granules, and wrinkled in front 

 subvertically; neck furrow shallow, moderately distinct, and con- 

 tinued across and round the side lobes, becoming very shallow as 

 it reaches the borders, and continuing so in its frontal extension; 

 neck ring distinct, ends nodular; axial furrows distinct and 

 wide and genal lobes sloping rather steeply into them; lateral lobes 

 subtriangular (equilateral), borders thickened, ridges along posterior 

 faces between the axial furrows and fulcra robust; imbricating 

 facets large; genal lobes highly convex and granulated, separated 

 from the palpebral lobes by a faint furrow"^ which passes pos- 

 teriorly around and under the eye, giving relief to that organ, 

 and joining the lateral prolongation of the neck furrow and 

 enclosing between them a suboblong tumose area or extension of 

 the genal lobe. Eyes very large, half as long as posterio-anterior 

 length of head, anteriorly almost resting on the cheek borders, being 

 separated from them by the fainter lateral furrows only; normal 

 number of vertical rows of lenses twent3''-two, closely packed, toler- 

 ably convex, with twelve lenses in each of the central rows, the total 

 number of lenses in each eye being about 220; in the cups the 

 attachment processes visible under a lens; cornea seems to have 

 been thin; lentiferous face curved from front to l^ack lunately, 



* This may be termed the palpebral furrow, and should perhaps be con- 

 sidered a generic character. 



