The Corals of Dela field . 187 



The genus is thus described by Dr. Hall : " A foliaceous branch- 

 ing coral, supported by smooih rootlike expansions ; branches 

 bifurcating and sometimes coalescing, celluliferous on both sides, 

 with thin central axis. Cellules, oval tubes, not enlarged below 

 apertures, distinctly oval with raised borders, nearly as wide as 

 the cells within. 



The distinctive features of these species lie in the mode of 

 branching, size, shape and arrangements of the cells. Their re- 

 semblance to modern Bryozoan forms is manifest. This resem- 

 blance is still more plainly seen in the reticulated forms represented 

 by Figs. 8 and 4.^ These are incrusting forms with the cells on 



' These figures refer to drawings placed before the association at the pres- 

 entation of this paper in December, 1878. Some of the corals will be illus- 

 trated in Vol. IV, Wis. Geol. Surv. 



one side only. Fig. 3 is an undescribed species, referred to the 

 genus Reiopora by Professor Whitfield. Fig. 4 was described 

 by Professor Whitfield, and his description is found in the annual 

 report of the Wisconsin Geological Survey for 1877, p. Q'6^ under 

 the name Fenestella granulosa. 



The more obvious characters of each form are as follows: The 

 Retopora presents anastomosing branches with irregular, elliptical 

 or linear, pointed meshes, upper surface of branches thickly covered 

 with circular pores which are arranged in three or four longitudinal 

 rows. In the Fenestella the branches do not reunite after separa- 

 tion, but frequently bifurcate and are connected at quite regular 

 intervals by extremely narrow bars which divide the interspaces 

 into ob'ong spaces or fenestrules. The pores in this form are ar- 

 ranged in lines, a single row on each margin of the branches or 

 rays. The opposite surface of the frond is densely covered with 

 very minute granules, hence the term granulosa^ applied to the 

 species. 



Turning to those forms which more closely resemble living 

 radiate corals, we notice first of all the delicately formed 

 Tremaiopora annulifer^ Whitfield, described in the Annual Re- 

 port Wisconsin Geological Sarvey for 1877, page 67. Scores 

 of fragments of this beautiful fossil are found imbedded ia 



