CORALS AND BRYOZOA. 267 



length of an aperture ; the apertures forming the rows are closely disposed, 

 the pustules being in contact and giving to the apertures the appearance of 

 being situated on curved elevations or ridges. The marginal apertures are a 

 little larger than the others, having a length of about .25 mm. Peristomes 

 thin, the posterior portion a little the more prominent and having two 

 slight denticulations. There are no longitudinal striations on the specimens 

 observed. 



Formation and locality. Hamilton group. Hill's gulch, four miles south of 

 Le Roy, New York. 



ACROGENIA, Hall. 1881. 



ACROGENIA PROLIFERA. 



PLATE LXIII, FIGS. 7-15. 



Acrogenia prolifera. Hall. Trans. Albany Institute, voL x, p. 194. 1881. 



" Report of State Geologist for 1883, p. 52. 1884. 



ZoARiUM ramose, branches flattened, proliferous. One frond, which is very 

 well preserved, has the following manner of growth : the basal extremity 

 for the space of 5 mm. is simple, with several lateral rootlets ; it is strongly 

 striated, and has a diameter of about 1.25 mm.; this portion bifurcates, the 

 two parts very gradually diverge and have frequent lateral striated rootlets, 

 the striae somewhat spirally disposed ; the ends are conically truncated ; 

 from these truncated ends proceed two short growths, both extremities of 

 which are conically truncated ; from the apices of these proceeds a striated, 

 cylindrical stipe, conically truncated at each end, and having a length of 

 8 mm., and a diameter of 2 mm.; the striae are of unequal strength, some of 

 them extremely fine : from the truncated apex of this stipe proceed apparently 

 several branches with conically truncated bases which are at first cylindrical, 

 becoming flattened and very gradually expanding: from this point the 

 growth is regular, two depressed, quadrangular branches proceeding from 

 the truncated extremity of each preceding branch ; length of internodes 



