246 



TRILOBITA 



CHAP. 



projection nearly as far as the posterior end of the thorax. The 

 glabella is convex and does not reach the front margin. The 

 cheeks are less convex than the glabella, and bear eyes which 

 usually consist of two or three lenses. An eye-line connects 

 the eye with the anterior part of the glabella. A suture is stated 

 to occur at the external margin of the flat border. The thorax 

 consists of from twenty-five to twenty-nine segments ; its axis is 

 narrow, and the pleurae are long and grooved. The pygidium is 

 very small, and consists of three or four segments. Ordovician 

 to Devonian. Genus : Harpes. 



Fam. 5. Paradoxidae (Figs. 147, 148, 149). The cephalic 

 shield is large, and bears long genal spines. The glabella is more 



FIG. 147. Paradoxides bohemicus, 

 I lair, x i. Middle Cambrian. 

 (After Zittel.) 



FIG. 148. Holmia ty'erulfi, Linnars. 

 x 1. Lower Cambrian. (After 

 Holm.) 



or less swollen in front. The facial sutures appear to be absent in 

 some genera, and when present extend from the posterior to the 

 anterior margin. The palpebral lobes are long, and often more 

 or less semicircular or kidney-shaped. The thorax is long, and 

 consists of from sixteen to twenty segments with their pleurae 

 produced into spines. The pygidium is very small, and plate-like, 



