590 HISTORICAL GEOLOGY. 



not known in New York, besides two at Mackenzie River. But in Nevada, 

 10 per cent occur in both the Lower and Upper 500 feet of the limestone ; 

 and 11 per cent of the Lower Devonian are known only in the Middle or 

 Upper of New York. Many species, therefore, were in existence over the 

 central and west-central portion of the continent before they reached, by 

 migration, the shallower waters of New York and Pennsylvania on the 

 eastern border of the Continental Interior. The species include about 25 of 

 Corals, numerous Brachiopods, Lamellibranchs and Gastropods, very few 

 Cephalopods, Trilobites and Crustaceans, and no Eurypterids or Fishes. 



Characteristic Species. 



Plants. — On Nematophyton and other Devonian plants see Dawson's G. Hist. 

 Plants, 1888; Trans. Boy. Soc. Can., 1889; also on other Devonian (Erian) Flora, 

 the Report in the Geol. Survey of Canada, 1871 ; also earlier, Q. J. Geol. Soc, vols. xv. 

 xviii,, xix., xxvii. Dawson also reports a species of Leptophloeum from the Lower Gaspfe 

 beds or Upper Helderberg. Drepanophycus of Goppert (1852), described as a seaweed, 

 has been shown to be the same as Psilophyton. The supposed fruit of Ghara is still of 

 doubtful nature. See Knowlton, Am. Jour. Sc, xxxvii., 1889. 



Animals. 1. Spongiozoans. — Species of Astrieospongia, and Hindia; Ischadites 

 ftwrsi/bj-mis H., Schoharie grit; Stromatopora potiderosa l!iich., Ohio; Syringostroma den- 

 sum and S. columnare Nich., Ohio. 



2. Actinozoans. — Fig. 858, Zaphrentis gigantea Raf., and 859, Zaph. Bafinesquii E. 



6 H., from the Falls of the Ohio, Z.Edwardsi Nich., Ohio, Z. prolifica B., Ohio ; another 

 Coral, of the genus Chonophyllum ( G. magnificum B. ) , has a diameter at top of 6 or 



7 inches ; it is from Walpole, Canada West. Fig. 860, Phillipsastrea Verneuili E. 

 & H., P. gigas Owen, Iowa, Ohio; Gystiphyllum Americanum E. & H., Heliophyllum 

 Haiti, E. & H. ; Fig. 861, Cyathopyllum rugosum H., fragment from a large mass. Falls 

 of the Ohio; Fig. 862, Favosites Goldfussi D'Orb., Falls of the Ohio, a fragment; F. tur- 

 binatus B., Canada, Ohio; Fig. 863, Syringopora Maclurii B., Canada, Ohio; Fig. 864, 

 Bom,ingeria cornuta B., from Canada. 



3. Hydrozoans. — Of the genus Dictyonema. 



4. Echinoderms. — Species of Dolatocrinus, Megistocrinus. Of Blastoids (Pentremites), 

 Fig. 865, Nucleocrinus Verneuili L. & C. 



6. MoUuscoids. — (a) ^ryo^oans are represented by many species of Fenestella and 

 other genera. 



(6) Brachiopods. — Figs. 866, 867, Spirifer acuminatus. Con., N.Y., Ohio, Ind. ; Fig. 

 868, Spirifer gregarius Clapp, N.Y., Ind., Ky., Falls of the Ohio; Leptcena rhomboidalis, 

 Wilckens, Canada. Also, Pentamerella arata Con., N.Y. and the West, Atrypa reticu- 

 laris Tumn., A. impressa H., A. aspera H. var. occidentalis, Amphigenia elongataY&ji., 

 Chonetes hemisphericus H., C. lineatus Van., Productella navicella H. Meristella nasuta 

 Con., N.Y. and the West. 



6. Mollusks. (ffl) Lamellibranchs. — Fig. 871, Paracyclas proavia Gdldt. (elliptica'H..), 

 N.Y., Ohio, Ind. Fig. 872, Conocardium cuneus Con., Ohio, Ind. ; Solenomya vetusta 

 Meek, the first known species of the genus, Ohio. 



(6) Pteropods. — Tentaculites scalariformis H., N.Y., Ohio, Ind., Hyolithes ligea H.; 

 Gonularia elegantula Meek. 



(c) Gastropods and Cephalopods. — Fig. 873, Platyceras dumosum Con. , from New 

 York and Columbus, Ohio. A dozen species of Platyceras have been described, and 5 or 6 

 or more of each Platystoma, Euomphalus, Loxonema, Pleurotomaria, Murchisonia, 



