CORALS AND BRYOZOA. 261 



stomes thin, equally elevated, not denticulated. Ranges of apertures near the 

 middle of the branch separated by a smooth, narrow ridge. When seven 

 ranges of apertures occur the ridges nearest the middle of the branch are 

 more prominent than the others ; when six ranges, the central ridge is the 

 most prominent, sometimes having the appearance of a carina, the two outer 

 ranges of each margin are not separated by ridges. 



********* 



Formation and locality. Hamilton group, shores of Seneca lake, Seneca 



county, N. Y. 



Stictopora subcarinata. 



PLATE LXIII, FIGS. 1-8. 



Stictoporaf tvbcarinata. Hall. Trans. Albany Institute, vol. x, p. 191. 1881. 



" (». g. f) dickotoma. Hall. By eiTor. Report of State Geologist for 1883, p. 48. 1884. 



ZoARiUM consisting of a flattened, dichotomously branched frond, arising from a 

 spreading base, or from several rootlets attached to foreign bodies ; distal ex- 

 tremities obtusely angular ; for a few mm. above the base the stipe is slender, 

 width less than 1 mm., having only two or three ranges of cell apertures ; 

 the frond then somewhat abruptly widens and becomes more flattened ; 

 branches above a bifurcation about 2 mm wide, very gradually and regu- 

 larly increasing to 2.50 mm. before bifurcating; non-celluliferous marginal 

 space a little less than .50 mm. wide ; margins sometimes crenulate ; 

 transverse section lenticular, abruptly contracting and very thin near the 

 margins, the intermediate portion convex or sub-angular; bifurcations on 

 the specimens observed occurring at intervals of from 4 to 10 mm. ; 

 branches diverging at an angle of about forty-five degrees. Cells tubular, 

 for a portion of their length recumbent, then abruptly curving and open- 

 ing directly or obliquely outward ; the cells at the middle of the branch 

 have a direction parallel with the longitudinal axis, becoming more and 

 more oblique as they approach the margin, where they are occasionally 

 nearly rectangular to the axis. The intercellular tissue consists of irregu- 

 larly disposed vesicles. Cell apertures oval, arranged in essentially parallel, 

 longitudinal rows, and very frequently in oblique, ascending rows from the 



