514 HISTORICAL GEOLOGY. 



from Kentucky ; Figs. 646, 646 a, Prasopora li/cuperdon ; Halysites catenulatus or related. 

 Galena limestone, and in Canada ; Tetradium columnare H. , Tennessee. 



3. Hydrozoans. — Fig. 647, Diphiyraptus (implexicanlis H., New York and Tennessee ; 

 647 a, enlarged; Climacograptus ; Strumatocerium pustitlosum Safi., Tennessee. Soleno- 

 pora compacta B., Canada, eastern New York, Kentucky, looks like a pebble, and a 

 limestone made largely of them resembles a conglomerate. It occurs abundantly at 

 Pleasant Valley, in Dutchess County, N.Y. (D wight). 



4. Echinoderms. — Fig. 648, PaUnaster matutinus 11., of the Trenton ; 649, TcBiiiaster 

 spinosus B. ; the Crinoids, Taxocrinus elegans B. (Fig. 650), Agelacrinus Billingsi Chap- 

 man, Glyptocrinus decadactylus H., Kentucky, Schizocrinus nodosus H., Heterocrinus 

 Canadensis B. ; also species of genera Hybocrinus, Porocrinus, Palmocrinus ; and the Cys- 

 toids, Comarocystites Shumardi M. & W., Missouri, C. punctatus B., Canada ; Dendrocrinus 

 retractilis Wale, Trenton Falls, Calceocrinus Barrandei Wale, ibid. ; Merocrinus typus 

 Wale, ibid., locrinus crassus H., ibid. ; Fig. 651, Pleurocystites filitextiis B., Amygdalo- 

 cystites, Kentucky. 



5. MoUuscoids. — (a) Bryozoans. — Species of Stictopora and Ptilodictya (related to 

 Figs. 629, 630) are common ; Clathropora Jiabellata H. ; Stomatopora arachnoidea H. 



(b) BracMopods. — Figs. 656, 657, Orthis biforata Schl. ; 658, 0. occidentalis H. \ 

 659, 0. testudinaria Dalm. ; 660, 0. tricenaria Con., 0. disparilis H., 0. subquadrata H., 

 and others ; 661, Leptcena (Plectambonites) sericea Sow. ; 662, Leptcena rhomboidalisWilc. ; 

 663, Strophomena {Bafinesquina) alternata Con., 8. incrassata H. ; 664-666, Bhynchonella 

 capax Con. ; 667, 667 a, Cyclospira bisulcata Emm. ; Zygospira modesta Say ; 668, 

 Schizocrania filosa H. ; Crania scabiosa H., Galena limestone; 669, Lingula quadrata 

 Eichw., and other species ; also species of Orbicidoidea, Treinatis, etc. 



6. Mollusks. — (a) Lamellibranchs. — Tellinomya alta H., Wisconsin, etc. ; ^4m- 

 bonychia attenuata H., Wisconsin, and others ; Conocardium imviaturum B., Black River 

 limestone, Ottawa ; Modiolopsis faba H., M. superba Bill., Wisconsin, etc.; Cypricardites 

 Niota H., Wisconsin, C. rectirostris. 



(6) Gastropods. — Fig. 673, Baphistoma lenticulare Emm., very common; Pleuro- 

 tomaria subconica H. , and other species; 674, Murchisonia Milleri; 675, M. bellicincta 

 H., often 4 inches long, 31. gracilis H., 31. tricar inata H. ; 676, Helicotoma planulata 

 Salter, Canada, Cyclonema bilix Con., Opliileta Oioenana M. & W., Galena limestone; 

 67^, Bellerophon bilobatus Sow., common; 678, same, side view; 679, Cyrtolites com- 

 pressus Con.; 680, 681, Cyrtolites (?) Trentonensis Cow. ; species of 3fetoptoma, a genus 

 which began in the Cambrian, Holopea, Trochonema, Eunema, Subulites, etc. Maclurea 

 magna (Fig. 634), Trenton of middle Tennessee (Safford) ; Chiton Canadensis B. is a 

 3'Ietoptoma, Black River limestone, Canada. 



(c) Pteropods. — Pteropods were represented by the earliest known of the straight, 

 slender shells called Tentacidites ; T. incurvus of Shumard is from Trenton beds in 

 Missouri and T. Sterlingensis and Oswegoensis of M. & Worthen and T. Bichmondensis 

 of Miller, from the Cincinnati group. There were also Conularise, and species of the 

 Theca family. Fig. 682, Conularia Trentonensis H. ; Pterotheca attenuata H. ; Theca 

 parviuscida H., Wisconsin ; Hyolithes, frequently having septa within in the smaller 

 extremity. 



(rZ) Cephalopods. — Fig. 683, Orthoceras jnncemn H. ; 0. anellum Conr., (Cycloceras 

 anellum of Hyatt) ; 684, 0. olorus H. ; 685, Actinoceras Bigsbyi of Bronn is Ormoceras 

 tenuifilum of Hall, from the Black River limestone ; good specimens show a transverse row 

 of foramina in each of the subdivisions of the beaded siphuncle, common in the Black 

 River limestone; Endoceras proteiforme H., Gonioceras anceps H. Endoceras (Kepas, 

 horn, and €v8ov, within) has a concentric structure of cone within cone in the siphuncle. 

 Fig. 686, C?/J'toceras subannulatum T>''Oi:'b. ; a, a transverse section; Fig. 687, Trocholites 

 undatus Hyatt = Lituites undatus Hall, from the Black River limestone, referred to 



