TRILOBITA—HYPOPARIA. 



259 



9. T. concentricus (Eaton). (Fig. 1547.) Ordovicic. 



Glabella finely granulated, produced posteriorly into a spine. 



Trenton-Lorraine of Canada, New York, New Jersey, Okla- 

 homa, Nevada, etc. 



V. Ampyx Dalman. 

 Thorax and pygidium resembling Trinucleus. Cephalon sub- 

 triangular without pitted border. Glabella large, elongate, enlarg- 

 ing anteriorly to the end of the cephalon, beyond which it is often 

 produced into a spine (rostrum). Genal angles spiniform. Ordo- 

 vicic and Siluric. 



(a) Ampyx restricted. — Glabella oval, terminating in a round 

 spine. Thoracic segments six. 



(b) Lonchodomus Angelin. — Glabella lanceolate, terminating in 

 an elongate, prismatic spine. 



10. A. (Lonchodomus) normalis Billings. Ordovicic. 

 Differs from A. halli in having the fixed cheeks extend to the 



base of the rostrum. 



Upper Quebec group (Div. N and P, Chazy) of Newfoundland. 



Fig. 1548. Loncho- Fig. 1549. Lonchodomus FiG. 1550, Ampyx 



domus halli. Top and halli. Top and end view of niagarensis^ cephalon. 



side view of cephalon, pygidium, X 3- (After Ray- (After Van Ingen.) 



X2. (AfterRaymond. ) mond. ) 



11. A. (Lonchodomus) halli Billings. (Figs. 1548, 1549.) Ordovicic. 

 Glabella rather sharply carinated along its top, and extending 



half its length beyond the anterior margin of the fixed cheeks, 

 beyond which it is prolonged as a prismatic spine with a furrow 

 on each of its four sides. Pygidium very broadly triangular, its 

 flat border abruptly bending downward at nearly a right angle. 

 Chazy of Vermont, New York and Quebec. 



12. A. niagarensis Van Ingen. (Fig. 1550.) Siluric. 

 Glabella ovate. 



Niagaran of Arkansas. 



