LICHAS (METOPOLICHAS) MARGINATUS. 105 



converging posteriorly and nearly reaching back to the occipital furrow ; in shape 

 they are pointed in front but truncated at their posterior end, which is incompletely 

 denned. The first lateral furrows are long, bend back strongly at first and con- 

 verge posteriorly at about 30°, but near their extremities suddenly turn outwards and 

 terminate blindly not far in front of the occipital furrow, into which they are 

 continued by a shallow groove. The central lobe is narrow near the base of the 

 bicomposite lobes, but widens anteriorly, expanding suddenly in front of them to 

 four times its basal width, so as to completely overlap and overhang the lateral lobes. 

 The fourth lateral lobes are almost obsolete. A pair of occipital lobes is 

 present ; in shape they are oval, narrow, transversely elongate, and less than half 

 the width of the neck-ring. The axial furrows are well marked and continuous, 

 curving inwards strongly about the middle of the lateral lobes and reaching the 

 occipital furrow nearly at the middle of the occipital lobes. The occipital furrow 

 is strong, wide, and gently arched. The occipital ring is broad, and has a median 

 tubercle. 



The fixed cheeks consist each of (1) a convex subreniform posterior portion 

 extending only half the length of the bicomposite lobes and having only half their 

 width ; and (2) a narrow flattened anterior wing joining the flattened striate and 

 coarsely tuberculate frontal border of the head-shield. The eye-lobe is semi- 

 circular and prominent, with its anterior end on the axial furrow opposite the 

 middle of the bicomposite lobe, and is separated from the convex subreniform part 

 of the fixed cheek by a strong sigmoidal eye-furrow running back obliquely, and 

 curving outwards posteriorly. The head-shield is ornamented with coarse, round, 

 sub-equal and closely placed tubercles, with a few smaller round ones intermixed. 

 Dimensions. — 



Length of head-shield . . . 25'0 mm. 



Width ,, between facial sutures . 22*0 „ 



Length of glabella .... 20*0 „ 

 Width „ at base . . 4- 5 „ 



„ „ at front . . . 19*0 „ 



Length of convex portion of fixed cheek . . 6'5 „ 



A large subcircular hypostome, measuring 14 mm. in length by about the same 

 in width, is in Mrs. Gray's collection from the same horizon and locality, and 

 probably is referable to the same species. It has a wide flattened border, swollen 

 a little on each side behind the lateral notches, which lie just behind the 

 small triangular anterior wings ; and its posterior edge is excavated by a broad 

 rounded notch, giving the characteristic bilobate shape. The body is subquadrate, 

 with subparallel sides; the axial furrows are nearly straight; the posterior 

 bounding furrow is weak, and truncates the body nearly at right angles to the 

 axial furrows. In front the outline of the body is arched forward. The body is 

 swollen anteriorly, but depressed behind the pair of very oblique, long, lateral 



14 



