ARTHROPODA. TRILOBITA. 201 



united to the front of the glabella by a straight ridge. 

 Thorax of from twelve to fifteen segments, pleurae 

 pointed. Pygidium small. Lingula Flags to Tremadoc 

 Beds. 



Paradoxides. Body large, elongated, narrowed pos- 

 teriorly. Head-shield broad, semicircular, with a border, 

 and long genal spines ; glabella elongated in front, with 

 two to four furrows on each side. Facial sutures extend 

 from the posterior to the anterior border. Eyes well 

 developed. Thorax long, formed of sixteen to twenty 

 segments; pleurae grooved and produced into long back- 

 wardly directed spines. Pygidium very small, axis of two 

 to eight segments. Harlech Beds to Lingula Flags. 



Olenellus. Similar to Paradoorides ; but differs in 

 the glabella not expanding in front, in the facial suture 

 being invisible, in having only thirteen or fourteen seg- 

 ments in the thorax, and in the absence of lateral lobes on 

 the pygidium. Lower Cambrian. 



Conocoryphe (= Conocephalites). Head-shield semi- 

 circular, without , genal spines ; axal furrows deep, gla- 

 bella narrow in front, and with three or four backwardly 

 directed furrows; free cheeks small. Facial sutures not 

 continuous in front and ending near the genal angles. 

 Thorax with fourteen or fifteen segments. Pygidium 

 small, margin entire, axis with from two to eight segments. 

 Harlech to Tremadoc Beds. 



Angelina. Body oval. Head-shield with long genal 

 spines, glabella without furrows; eyes small, near the 

 middle of the cheeks. Thorax with fourteen or fifteen 

 segments, pleurae facetted. Pygidium short, margin pro- 

 vided with two teeth, axis formed of four or five segments. 

 Tremadoc Beds. 



