522 



MOLLUSDOIDA. 



[sCE. — SEP. 



luliferous on each face ; cells radiating 

 from the center to each angle of the 

 branch ; margins and summit of lam- 

 inae noncelluliferous. Type S. scalari- 

 formis. 



approximata, Ulrich, (in press,) Geo. Sur. 

 111., vol. 8, pi. 43, Ham. Gr. 



scalariformis, Hall, 1881, Brvozoans of 

 Up. Held. Gr., p. 18, and Pal. N. Y., 

 vol. 6, p. 100, Up. Held. Gr. 



separata, Ulrich, (in press,) Geo. Sur. 

 111., vol. 8, pi. 43, Ham. Gr. 



subconcava, Hall, 1881, Bryozoans of Up. 

 Held. Gr., p. 18, and Pal. N. Y., vol. 6, 

 p. 100, Up. Held. Gr. 

 Scenellopora, Ulrich, 1882, Jour. Cin. 

 Soc. Nat. Hist., vol. 5, p. 150. [Ety. 

 scene, tent; ellus, diminutive; poros, 

 pore.] Zoarium broad, obconical ; cell 

 apertures on ridges, which radiate from 

 the subsolid and depressed center of 

 the upper surface. Type S. radiata. 



radiata, Ulrich, 1882, Jour. Cin. Soc. Nat. 

 Hist, vol. 5. p. 158, Trenton Gr. 

 ScEPTrvOPORA, Ulrich, 1888, Am. Geo., vol. 

 1, p. 228. [Ety. skeptron, staff; poros. 



Fig. 513— Sceptropora facula, x 18. «, Segment: 

 e, transverse section ; d, transverse section of 



pore.] Zoarium articulated; segments 

 short, numerous, club-shaped, lower 

 half striated, noncelluliferous; upper 

 half expanded, celluliferous, and hav- 

 ing one or more articulating sockets; 

 zocecia subtubular, radially arranged 

 about a central axis; apertures sub- 

 ovate. Type S. facula. 



facula, Ulrich, 1888, Am. Geo., vol. 1, p. 

 228, Hud. Riv. Gr. 

 Selenopora, Hall, 1887, Pal. N. Y., vol. 6, 

 p. xvii. [Ety. selene, moon ; poros, pore.] 

 Zoarium explanate, incrusting; aper- 

 tures subcircular, with an elevated den- 

 ticulate peristome, and situated within 

 polygonal vestibular areas formed by 

 connecting walls, which traverse the 

 surface ; interior structure as in Liche- 

 nalia. Type S. circincta. 



circincta, Hall, 1881, (Lichenalia circincta,) 

 Trans. Alb. Inst., vol. 10, p. 11, and 

 Pal. N. Y., vol. 6, p. 86, Up. Held. Gr. 



complexa, Hall, 1881, (Lichenalia com- 

 plexata,) Trans. Alb. Inst., vol. 10, p. 

 11, and Pal. N. Y., vol. 6, p. 87, Up. 

 Held. Gr. 



Semicoscinium, Prout, 1859, Trans. St. Louis 

 Acad. Sci., vol. 1, p. 443. [Sig. some- 

 what like Cosciniurn.] Leaf-like expan- 

 sion, somewhat penniform, without a 

 shaft; sole formed of longitudinal and 

 horizontal parallel ridges, surmounted 

 by a cellular tissue, divided perpendic- 

 ularly by thin, longitudinal septa, cor- 

 responding to the ridges, and support- 

 ing parallel lines of tortuous tubes 

 alternately approximating and receding 

 from each other; covert d by a dense, 

 strong crust, divided into a net-work of 

 rays and dissepiments bounding rhom- 

 boidal or ovate fenestrules, giving pas- 

 sage to oblique cells; the tortuous tubes 

 give place to quincuncial, oval openings 

 in the fenestrules; each tortuous tube 

 has a line of cells on each side. Type 

 B. rhomboideuin. 

 eriense, Prout, Trans. St. Louis Acad Sci., 



vol. 1, p. 579, Up. Held. Gr. 

 obliquatum, Ulrich, 1886, Cont. to Am. 



Pal. p. 13, Up. Held. (Jr. 

 planodorsatum, Ulrich, (in press,) Geo. 

 Sur. 111., vol. 8, pi. 45, Up. Held. (ir. 



rhomhoideum, Prout, 

 1859, Trans. St. 

 Louis Acad. Sci., 

 vol. 1, p. 443, Up. 

 Held. Gr. 

 rhombicum, Ulrich, (in 

 press,) Geo. Sur. 111., 

 vol. 8, pi. 45-54, 

 Ham. Gr. 

 tuberculatum, Prout, 

 1 si id, Trans. St. Louis 

 Acad. Sci., vol. 1, p. 

 579, Up. Held Gr. 

 Semiopora, Hall, 1884, 

 Rep. St. Geol., p. 51. 

 [Ety. semi, half; 

 poros, pore.] Bryo- 

 branches infrequent, bi- 

 furcating or tribifurcating; margins par- 

 allel ; celluliferous on both sides ; cells 

 arising from a mesial epitheca; aper- 

 tures in longitudinal parallel rows, sep- 

 arated by ridges; two minute pits on 

 the transverse space between adjacent 

 apertures; apertures near the margin 

 larger and more oblique than the 

 others; margin striated; noncellulifer- 

 ous. Type S. bistigmata. 

 bistigmata, Hall, 1884, Rep. St. Geol., p. 

 57, Ham. Gr. 

 Septopora, Prout, 1859, Trans. St. Louis 

 Acad. Sci., vol. 1, p. 448. [Ety. septum, 

 partition ; porus, pore.] Zoarium like 

 Fenestella, but distinguished by the dis- 

 sepiments, which have from one to four 

 rows of cells. Type S. cestriensis. 

 cestriensis, Prout, 1859, Trans. St. Louis 

 Acad. Sci., vol. 1, p. 448, Kaskas- 

 kia Gr. 

 decipiens, Ulrich, (in press,) Geo. Sur. 



111., vol. 8, pi. 66, Kaskaskia Gr. 

 delicatula, Ulrich, (in press,) Geo. Sur. 

 111., vol. 8, pi. 64, Low Coal Meas. 



b, vertical section ; 

 expanded part. 



zoum ramose : 



