228 PALEOZOIC TIME. 



Characteristic Species. 



1. Medina Epoch. 



Fig. 398, Arthrophycus Harlani H. Occurs rarely in the Oneida conglomerate, vert 

 abundantly in the Medina beds. Fig. 399, Lingulella cuneata H. ; 400, Modiolopsis or- 

 thonota H. : 401, M. (?) primigenia EL ; 402, Pleurotomaria litorea H. ; 403, Bucanelln 

 trilobata Sow., different views. Orthocerata are ocasionally met with. The only Crus- 

 tacean described is the Ostracoid, Leperditia cylindrica Hising. 



2. Clinton Epoch. 



1. Radiates. — (a.) Polyps. — Figs. 405, 406, Zaphrentis [Caninia) bilateralls H. : 

 408 a branching Chcetetes. (b.) Acalephs. — 409, a, Oraptolithus Clintonensis H. (c.) 

 Echinoderms : Crinoids. — A few species are known : fragments are common, and they 

 are often found in the iron-ore, as well as in the limestones. Echinoids. — Fig. 407, 

 Palceocyclus rotuloides H. , a small species. 



2. Mollusks. — ■ (a.) Bryozoam. — Fig. 410, Fenestella (?) prlsca Lonsdale. 



(b.) Brachiopods. — There are species of Lingulella, Orthis, Leptcena, Rhynchonella, 

 Spirifer, and also of the new genera for America, Chonetes and Pentamerus. Fig. 411, 

 Pentamerus oblongus Murch. ; some specimens are more than twice the size of this fig- 

 ure, and very thick; it is abundant in New York and the West, and occurs also in Great 

 Britain; Figs. 412, 413 show casts of the interior, — 412 a dorsal view, and 413 a ven- 

 tral. Figs. 414, 415, Atrypa reticularis Linn., or a related species; the A. reticularis is 

 reputed to extend through the Niagara period into the Hamilton of the Devonian ; but 

 more than one species are probably here included; this also is a foreign species: it is 

 one of the few species of true Atrypa ; the interior of the shell is shown in Fig. 225. 

 Fig. 416, Athyris (?) congesta Con.; Fig. 417, same, different view, — it has a spire 

 within, extending downward and outward; Fig. 418, Chonetes cornuta Koninck. 



(c. ) Lamellibranchs. — Fig. 419, Avicida rhoniboidea H. 



(d.) Gasteropods. — Fig. 420, Cyclonema cancellation H. Bucanella trilobata of the 

 Medina also occurs here, besides other Gasteropods. 



(e.) Cephalopods. — Species of Orthoceras. 



In the Anticosti beds, there are Cephalopods of the genera Orthoceras, Cyrtoceras, 

 Oncoceras, Ascoceras, Glossoceras, as well as Beatricea ; and Trilobites of the genera 

 Asaphus, Calymene, Illmnus, Phacops, Dalmanites, Encrinurus, Harpes, Lichas, etc., 

 and among these, Asaphus megistos and Calymene Blumenbachii. If the- so-called Bea- 

 tricea} were the internal bones of Cephalopods, as seems probable (after Hyatt's obser- 

 vations), some of these animals must have been 20 or 30 feet long. The fossils are 

 somewhat like a long straight branch of a tree, with an irregularly fluted or otherwise 

 uneven exterior, and have been described as remains of plants ; but they have a cone- 

 in-cone structure, with cellular interspaces about the center, and the plates in contact 

 toward the sides. They are from 1 to 14 inches in diameter. 



3. Articulates. — Eemains of Trilobites of the genus Homalonotus, and of the 

 same species figured under the Niagara epoch. Tracks or scratches occur, which have 

 been referred with good reason to Crustaceans, besides others like Fig. 422, that are 

 attributed to Worms. 



Among the Clinton species are the following from the Lower Silurian : Orthis lynx, 

 Leptcena sericea, Bellerophon bilobatus. The following are known in Europe: Orthis 

 lynx, Chonetes cornuta H., Atrypa reticularis, A. hemispherica Murch., Spirifer radiatus 

 Sow., Pentamerus oblongus. 



3. Niagara Epoch. 



1. Protozoans. — Sponges of the genera Astraospongia, Astylospongia and Pala- 

 omanon in Tennessee; they occur in the upper part of the Niagara (or Meniscus) lime- 



