164 TRILOBITES OF GIRVAN. 



the body, which is weakly convex and not marked off from them anteriorly, is 

 subcircular in shape, narrowing slightly behind, and the lateral wings extend along 

 half its length ; behind them is a border of moderate width, marked off on each 

 side from the body by a strong, slightly oblique furrow ; these furrows do not 

 meet behind, and apparently are composed of the marginal and lateral furrows, as 

 they bend inwards more strongly at their posterior ends ; behind them the body is 

 not marked off from the border. The whole surface of the hypostome is orna- 

 mented with fine, wavy lines concentric to the posterior and lateral margins and 

 meeting the anterior margin at a more or less acute angle. The type of hypostome 

 is that of /. chiron, Holm, /. esmarhi, Schloth., etc. 1 

 Dimensions. — 



Length . . . . .7 mm. 



Width at front end . . . . 12 ., 



lllaenus bowmani, [Salter. Plate XX, fig. 10. 



1904. Illsenus bowmani, Reed, sajira, p. 59. 



There is an interesting specimen of /. bowmani from the Starfish Bed which 

 shows the whole individual both as a cast and a hollow mould, though neither is 

 quite perfect. But the most important feature is the preservation f the hypo- 

 stome in its natural attachment to the epistome, though it does not lie in the 

 normal plane, having been bent back underneath the latter. The epistome is 

 broken laterally, but appears to have had the usual transverse fusiform shape 

 without any marked posterior protuberance, and it is crossed by 12 — 14 strong, 

 equidistant, scarcely curved, strige. The hypostome is subquadrate in shape, wider 

 than long, and arched down on each side. The anterior margin is a flattened 

 curve, but the lateral angles are rounded, the anterior wings being placed far 

 back and nearly opposite the middle of the body. The body itself is subquadrate 

 and moderately convex, and has a pair of rather large lateral pits a little behind 

 its middle, and there is a faint shallow depression connecting them and curving 

 round behind the body so as to mark off indistinctly a posterior border. The 

 posterior end of the hypostome is broad and obtuse. 



A few fine, irregular, raised lines are visible on the ahe, but the ornamentation 

 is not preserved on the rest of the surface. 



Dimensions. — 



Length of hypostome . . . U'O nun. 



Width ,, across anterior ahe . 19"0 ,, 



„ „ behind ahe . . lO'O „ 



1 Lindstrom, 'K. Svensk. Vet. Akad. Handl.,' vol. xxxiv, no. 8 (1901), p. 58, pi. iv, figs. ±2— 38. 



