MARYLAND GEOLOGICAL SURVEY 223 



order CRY PTOSTOM ATA 



Family PTILODICTYONIDAE 



Genus ESCHAROPORA Hall 

 ESCHAROPORA CONFLTJENS Ulrich 



Plate XL, Figs. 11-14 



Escharopora confluens Ulrich, 1893, Geol. Minnesota, vol. iii, p. 171, pi. xiil, 

 figs. 1-11. 



Description. " Zoarium branching, the smallest seen less than 25 mm. 

 high, with the branches averaging about 2.5 mm. in width; the largest 

 fragments indicate a hight of from 80 to 120 mm., and in these the width 

 of the branches varies from 4 to 8 mm. The two surfaces of the branches 

 are generally obtusely ridge-shaped, and in the largest a row of monti- 

 cules, or simply clusters of large cells, occurs on the summit of the ridge. 

 Edges thin and sharp, commonly with a coarsely striated or pitted narrow 

 border. Through all stages, though less distinct in the oldest, the 

 zocecial apertures are narrow and appear to be drawn out at the ends so 

 as to connect by means of a narrow channel. This confluent character 

 of the zocecial apertures is better shown and more regular in the central 

 rows, where they are also narrower and on the whole considerably smaller 

 than toward the margins. In the central rows, 10 in 5 mm. lengthwise ; 

 18 or 19 in 5 mm. diagonally, and five and one-half in 1 mm., and 10 in 

 2 mm., transversely ; of longitudinal rows there are 19 or 20 in 2 mm. 



" Tangential sections show that the base of the zorecia, excepting those 

 in the marginal rows, is bounded by very thin, straight, longitudinal wall,, 

 and equally thin transverse partitions. This portion of the zocecium 

 therefore may be described as a parallelogram, with the length and 

 breadth respectively as four is to one. At about the middle of the hight 

 of the primitive cell its sides have spread a little and the ends contracted 

 in a corresponding degree. Just as the posterior half is about to be 

 roofed over two projections from the side walls, at a point a little behind 

 the middle, gradually converge until they meet and thereby cut off and 

 15 



