600 



Heport of the State Geologist. 



which have the same manner of growth as the primary rachis. 

 This mode of growth is continued indefinitely, the zoarium 

 frequently covering a comparatively large area. 



Cell tubes subcylindrical, slightly sinuous, especially near the 

 base ; the attached portion flat, the free portion convex. For a 

 short distance the cells are nearly parallel with the rachis, then 

 diverge at an angle of thirty- five or forty degrees; near the 

 aperture turning directly outward, so that the aperture is at right 

 angles to the main portion of the cell tube ; margins of the cell 

 tubes in contact, but not coalescing; the end of each succeeding 

 cell tube projecting beyond the preceding one, giving a serrate 

 appearance to the margin of the frond ; cell tubes annulated. 



Family Phaceloporidae, Ulrich. 

 This family at present includes one genus, Phaoelopoba. 



Phacelopora, Ulrich. 



(Geol. Sur. 111., p. 388. 1890.) 



Type, Phacelojpora pertenuis, Ulrich. 



Zoarium articulated, segments short, conical, consisting of two 

 or more equal conical cell tubes, with slightly contracted^circular 

 apertures. 



209 



X25 



x25 



Fig, 20?. Phacelopora pertenuis. Natural size, and x 25.1 

 Fig. 208. A vertical section of the same, x 25. 

 Fig. 209. P. constricta. A portion of a frond, x 25. 



