UPPER SILURIAN. 229 



stone. Roemer made out six species, of which Astrceospongia meniscus is the most abun- 

 dant. Fig. 428, Stromatopora concentrica H., a very minutely porous coral, often in 

 concentric layers. 



2. Radiates. — (a.) Polyps (Corals). — Fig. 423, Chonophyllum Niagarense H., 

 (Conophyllum of Hall, a genus first published in 1852, two years after Chonophyllum 

 by Edwards); 424, Favosites Niagarensis H. ; 424 a, surface of same, enlarged, show- 

 ing outline of cells; 425, Halysites catenulnta ; 420, Heliolites spinipora H. ; 427, an 

 enlarged view, showing the 12-rayed cells and the interval of a cellular character sepa- 

 rating them, both of which are distinguishing characteristics of the genus Heliolites. 



(b.) Echinoderms. — Fig. 429, Icthyocrinus Icevis Conrad, a species which is sometimes 

 wice as large as the figure; 430, Caryocrinus ornatus Say, of Lockport, the nut-like 

 shape having suggested the generic name (from Carya, the hickory-nut); 431, Stephan- 

 ocrinus angulatus Conrad, of Lockport; a, part of the stem, enlarged; b, joint of the 

 stem, top-view; c, base of the body, showing the three pieces of which it consists. 

 Also, Fig. 146 (page 117), the Cystid Callocystites JewettiiH., and Fig. 144, the Star- 

 fish Palceaster Niagarensis H. 



3. Mollusks. — (a.) Bryozcans. — Many species of delicate corals of the genus 

 Fenestella, resembling Fig. 410, and of other genera, (b.) Brachiopods. — Fig. 432, 

 Strophomena rhomboidalis Wahl. ; 433, Leptcena transversalis Dahnan; 434, Atrypa 

 nodostriata H., the Niagara form of this species; 435, same, side-view; 436, Merista 

 nitida H., 437, Anastrophia (or Brachymerus) interplicata H. ; 438, a, Rhynchonella 

 cuneata H. ; 439, a, b, Leptocodia disparilis H. ; 440, Orthis bilobusK.; 440 a, same, en- 

 larged; 441, Spirifer Niagarensis Con.; 442, same, side-view; 443, 444, Sp. sulcatus 

 Hising. Pentamerus oblongus (Fig. 411), a Clinton group species, is very abundant in 

 the Niagara limestone of the Mississippi basin. Among these, all but the Leptocozlia 



isparilis H , Atrypa nodostriata H. and the Orthis and Spirifers, are found also in 

 European rocks. 



(c.) Lamellibranchs. — Fig. 444 A, Megalomus Canadensis H., from the Gait, Canada; 

 445, Avicula emacerata Con. 



(d. ) Gasteropods. — Fig. 446, Platyostoma Niagarensis H. ; 447, Platyceras angula- 

 tum H. ; a, same in different position. 



(e.) Pteropods. — Conularwe, of different species. 



(f.) Cephalopoda. — Species of Orthoceros, Cyrtoceras, Gomphoceras, and Lituites, 

 which are common in the Interior basin. 



4. Articulates. — (a.) Trilobites. — Fig. 448, Dalmanites limulurus H. (a genus 

 differing from Calymene in having the glabella, or middle region of the buckler, largest 

 anteriorly, besides having large reniform eyes and other peculiarities); 449, Lichas Bot- 

 tom H., a large and characteristic species, much reduced; 450, Homalonotus delphino- 

 cephalus Murch. (the genus having very small eyes, the glabella faintly outlined and 

 undivided, — the middle lobe of the body much broader than the lateral); 451, Illce- 

 nus Barriensis Burmeister; Calymene Blumenhachii var. Niagarensis H., near Fig. 361 

 (page 202). (b.) Ostracoids, or bivalve Crustaceans. — Fig. 452, Beyrichia symmetrica 

 H., showing one of the valves; a, same, natural size. (c. ) Phyllopods. — Ceratiocaris 

 Deweyi Hall. The only specimens found in the Niagara beds are the spine-like ter- 

 minal joint of the body (formerly supposed to belong to a fish, and named Onchus 

 Deweyi). 



The following are some of the species common to the Niagara and Clinton groups: — 



Halysites catenulata (Fig. 425). Spirifer radiatus. 



Caryocrinus ornatus (Fig. 430). Avicula emacerata (Fig. 445). 



Hypanthocrinus decorus. Orthonota curta? 



Lingula lamellata. Modiolopsis subalata? 



Orthis elegantula (Fig. 389). Ceraurus insignis. 



Strophomena rhomboidalis (Fig. 432). Homalonotus delphinocephalus (Fig 450). 



Pentamerus oblongus (Fig. 411). Calymene Blumenbachii. 



Rhynchonella neglecta. Dalmanites limulurus (Fig. 448). 



Mrypa reticularis (Fig. 414). . Illaenus Barriensis (Fig. 451). 



