PHACOPS. o« 



Zd 



the axis raised above the sides, not separated by deep furrows except in the head, and 

 more convex in the thorax than in the head or tail. 



The head is less than a semicircle, though just twice as long as broad ; the general 

 outline rather triangular, from an indentation in the outer margin on each side of the 

 glabella ; the front is not produced, but angular. The glabella occupies more than one 

 third the width of the head in front. It has nearly straight, parallel sides, and rises con- 

 siderably above the cheeks, but is depressed rather than convex, especially the forehead- 

 lobe, which slopes gradually to the narrow marginate front. Neck -lobe strong, broader than 

 the first basal lobes, which are transverse and linear ; the middle pair are broader than 

 these, and oval. The lower furrow bends downwards, and reaches the side of the glabella ; 

 the middle one is abbreviated, and curves the reverse way. Upper lateral lobe transverse, 

 scarcely triangular, bounded above by a sigmoid furrow, which runs obliquely out above 

 the eye. 



All the furrows stretch equally towards the middle of the glabella, leaving but a 

 narrow space between their ends ; between the upper pair a short longitudinal depression 

 occurs. The lobes are not swelled between the furrows, but the surface is even, and the 

 furrows shallow (they are, however, sharply defined on the internal cast), the neck and 

 basal furrows strong ; the upper ones fainter. 



The cheeks are steeply bent down, their outer margin not distinguished by any furrow, 

 and they slope gradually from the eye, without any ridge or groove, beneath the latter ; 

 the neck-furrow is continued almost to the angle, which is rounded off, and has a tubercle 

 only in place of a spine. The facial suture cuts the outer margin in a curved line opposite 

 the base of the eye ; on the under surface of the head the suture cuts the margin further 

 backward (fig. b). In front of the eye it runs along the axal furrow and round the 

 glabella just outside the marginal furrow. It is thus what is called intramarginal. 



Eyes moderately large, in some specimens (figs. 18, 25, 26, 30) much larger than others ; 

 and they rise occasionally to the level of the glabella, but are generally lower. The eye is 

 not very prominent ; it is placed half-way up the cheek, near to the upper glabella-lobes, and 

 occupying their length ; eye-lobe with a raised outer margin ; lentiferous surface broad, 

 with about 155 lenses in the eye, each vertical row containing eight. The cornea is convex 

 over the lenses, and the intermediate flattened spaces are finely granular, the granules 

 forming a rough hexagonal network toward the base of the eye ; the lenses are nearly their 

 own diameter apart, but this varies much in different individuals, the space being often 

 much less. (Fig. 36,</, e.) 



On the under side of the head the incurved front portion, or hypodome, as in all the 

 genus, is continuous across ; it is broad (fig. 36, b) and granular, like the upper surface. The 

 labrum is also granulate j it is subquadrate, broadest at base, regularly and strongly convex ; 

 a faint concentric furrow runs round its sides and tip, just indicating a narrow margin 

 more flattened than the other parts ; there are no lateral furrows, but high up on each 

 side is a small tubercle. The tip is obtusely truncate, with no visible serratures. The 

 4 



