SUBCLASS 



TEILOBITA 



719 



Asaphellus Callaway. Similar to Megalaspis, but with longer and flatter glabella, 

 and shorter shields. Tremadoc ; Europe. Lower Ordovician ; North America. 



Hemigyraspis Raymond. Similar to Asaphellus, but with facial suture marginal 

 in front. Tremadoc ; Europe. Lower Ordovician ; North America. 



Sympliysurus Goldfuss. Cephalon and pygidium short, sub-hemispherical, without 

 concave border. Axial lobe narrow. Lower Ordovician ; Europe and America. 



Nileus Dalman. Similar to Symphysurus, but with broad axial lobe and very 

 large eyes. Ordovician ; Europe and North America. 



Subfamily B. Asaphinae Raymond. 

 Asaiihidae ivith hypostoma bifurcated. 

 AsaphiijS Brongniart (Figs. 1364, E ; 1384). Cephalon and pygidium short and 



(^% 



Fig. 13S4. 

 Asaphus expansus (Linn.). Ordovician ; Pulkowa, near St. Petersburg, Russia, i/i (after .Salter). 



wide, glabella prominent, expanding forward, and reaching 

 the anterior margin, which is without concave border. 

 Axial lobe of i:)ygidium ringed, pleural lobes smooth. 

 Ordovician ; Europe and Asia. 



Onchometopiis Schmidt. Similar to Asaphus, but the 

 glabella only obscurely defined, axial lobe rather wide, and 

 pygidium smooth. Ordovician; Europe and North America. 



Basilicus Salter. Pygidium strongly ribbed, glabella 

 convex, prominent, facial suture marginal in front. Ordo- 

 vician ; Europe and North America. 



Ogygites Tromelin and Lebesconte {Ogygia Brongniart) 

 (Fig. 1385). Similar to Basilicus, but glabella less pro- 

 minent, and sutures meeting in a point in front of glabella. 

 Ordovician ; Europe and North America. 



PtAjchopyge Angelin. Glabella short, facial sutures well 

 inside the margin, pygidium not ribbed, concave borders 

 wide, and doublure very broad. Ordovician ; Europe. 



Isotelus Dekay. Cejihalon and pygidium smooth, with 

 wide depressed borders. Axial lobe of thorax wide. Ordo- 

 vician ; rare in Europe, abundant in North America. 



Family 12. Illaenidae Corda. 



, Opisthoparia with large, convex cephalic and abdominal 

 shields which are nearly smooth and without concave border. 

 Epistomal plate large, hypostoma convex, ovoid. TJiorax of 

 eight to ten segments, tuith smooth pleura. Pygidium smooth, 

 with short axial lobe. Ordovician and Silurian. 



Illaenus Dalman (Figs. 1364, F ; 1386). Axial lobe 



Fio. 13S5. 



Oyygites guettardi (Brong.). 

 Ordovician ; Angers, France. 

 Mechanically deformed indi- 

 vidual (after Brongniart). 



