NIAGARA PERIOD — NIAGARA EPOCH. 



241 



(c.) Conchifers. — Fig. 405, Avicula emacerata. 



(d.) Gasteropoda. — Fig. 406, Platyostoma Niagarensis; 407, Platyceras angn- 



Figs. 392-404. 



Brachiopods.— Fig. 392, Strophomena rugosa; 393, Leptaena transversalis ; 394, 395, 

 Atrypa nodostriata; 396, Merista nitida; 397, Pentamerus interplicatus ; 398, a, Rliyn- 

 chonella cuneata; 399, a, b, Leptocoelia disparilis; 400, a, Orthis bilobus; 401,402, Spirifer 

 Niagarensis ; 403, 404, Sp. sulcatus. 



latum, a true univalve, but loosely and imperfectly coiled, as shown in the 

 profile view, fig. 407 a. 



Fieis. 405-407. 



Coxchifer and Gasteropods. — Fig. 405, Avicula emacerata; 406, Platyostoma Niagarensis: 

 407, a, Platyceras angulatum. 



(e.) Cep\alopods. — Species of Orthoceras, Cyrtoceras, Gomphoceras, and of 

 Gonularia. The last probably belongs to the division of Cephalopods having 

 internal shells. 



3. Articulates — (a.) Trilobites. — Fig. 403, Dalmama limiilurns (a genus 

 differing from Calymene in having the glabella, or middle region of the buck- 

 ler, largest anteriorly, besides having large reniform eyes and other pecu- 

 liarities) ; 409, Lichas Boltoni, a large and characteristic species, much reduced; 

 410, Homalonotus delphinocephalus (the genus having very small eyes, the glabella 

 faintly outlined and undivided, — the middle lobe of the body much broader 

 than the lateral); 411, Illsenus Barriensis ; Calymene Blumenbachii var. Niaga- 



17 



