DEVONIAN AGE. 261 



stone of the Black River limestone (p. 194), from Watertown, N. Y., 

 which affords also Desmids and spicules of Sponges.] 



Characteristic Species. 



1. Radiates. — (a.) Polyps. — Fig. 485, Zaphrentis gigantea ; Fig. 486, Zaph. Ra- 

 fnesquii E. & H., from the Falls of the Ohio. Another Cyathophylloicl coral, of the 

 genus Chonophyllum (C. maynificum B.), has a diameter at top of six or seven inches; 

 it is from Walpole, Canada West. Fig. 487, Phillipsastrea Vemeuili E. & H. : Fig. 

 488, Cyathophyllum rugosum, a fragment from a large mass from the Falls of the Ohio; 

 488 a, section of a cell; Fig. 489, Favosites Golclfussi D'Orb., from the Falls of the Ohio, 

 a fragment of a large specimen; Fig. 490, Syringopora Maclurii B., from Canada West, 

 a coral consisting of a cluster of small tubular cells; Fig. 491, Aidopora cornuta B., from 

 Canada. 



(b.) Acalephs. — No species are known, unless some of the Corals belong here. 



(c.) Echinoderms. — There are many species of Crinoids, and the large, smooth stems 

 of some of them are half an inch to an inch in diameter. Of the Nucleocrini (also called 

 Olivanites), Fig 492 represents the X. Vemeuili L. & C. The name Nucleocrinus of 

 Conrad antedates Olivanites Troost, and Eltzacrinus Koemer. 



2. Mollusks. — (a.) Brachiopods. — Figs. 493 and 494, Spirifer acuminatus Con. 

 {S. cultrijugatus Roemer), from New York and the West. Fig. 495, Spirifer gregarius 

 Clapp, very common in Indiana and Kentucky, at the Falls of the Ohio, and at Middle- 

 ton, Canada (Billings). Also, Pentamerella arata H., Chonetes hemisphcericaH., Atrypa 

 reticularis, A. impressa H., X spinosa H. (A. a$j)era), Ampkigenia elongata (formerly 

 Pentamerus elongatus Vanuxem, and Stricldandinia elongata Billings), Rhynchondla 

 venustula Hall {Atrypa cuboides of Sowerby, also Vanuxem), found in Tennessee. Two 

 small species of Productus have been collected by Billings in Canada, and one by 

 Jewett in the New York Corniferous. 



(b.) Lamellibranchs. — Fig. 496, Lucina (?) proavia Goldf., also occurring in Europe; 

 Fig. 497, Conocardium trigonale, of both New York and the West. The first known 

 species of Solenomya (Meek), and also of Orthonema, another Carboniferous genus. 



(c.) Pteropods, Gasteropods, and Cephalqpods. — Pteropods are represented by the 

 Tentaculites scalaris Schlot. There are also several species of Gasteropods. Fig. 498 is 

 the Pldtyceras dumosum Con., of the Corniferous in New York. 



A few Orthocerata occur in the beds. The Cyrtoceras undulatum, a large shell coiled 

 in a plane, is supposed, as the name implies, to be related to the Cephalopods. 



3. Articulates. — - Trilobites are the only Articulates known. The most common 

 species are the Dalmanites (Odontocephalus) selenurus H., having a two-pointed tail; 

 and the Proetus (Calymene) crassimarginatus H., having the posterior margin of the 

 body (the pygidium) thickened and rounded. There are also Phacops bufo H., and 

 some other species. 



The following species continue on into the Hamilton : Orthis Vanuxe/rii H. '? Sfrepto- 

 rhynchus Chemungens'S H., Strophodonta (Strophomena) demissa H., S. perplana H. 

 (— S. crenistria H.), Spirifer fimbriatus Con. (found also in the Oriskany, Atrypa im- 

 pressa H. (=var. of A. reticidaris), Phacops bufo. 



4. Vertebrates. — The remains of Vertebrates, under the form of 

 Fishes, appear first, in America, according to present knowledge, in 

 the rocks of the Corniferous period. The subdivisions of fishes rep- 

 resented are the same that have been distinguished in the foreign 

 Upper Silurian. They are the following, — 



1. The Shark-tribe or Selachians (so named from o-eXa^os, a carti- 

 laginous fish), the bones being cartilaginous or mostly so. In this 

 division, the gill-openings, as shown in Fig. 502, have no operculum. 



