GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 343 



specimens of P. crassoramosa, but have seen none of P. tenuis. 

 P. crassoramosa has thickish branches on which verrucae may be 

 well developed or obsolete; P. tenuis appears to be of more or less 

 massive growth-form and has across the corallite cavities thin 

 tabulae, the spaces between which are not filled by steroplasinic 

 deposit. 



I have specimens representing four additional American fossil 

 species of the genus. They are all branching forms. I collected 

 one of the species at Willoughby Bay, Antigua, in the Antigua forma- 

 tion; and another in the upper Oligocene marl at Baracoa, Cuba. 

 The specimen at the latter locality was obtained in association with 

 Stylophora granulata Duncan, which was originally described from the 

 Bowden marl of Jamaica. Miss Carlotta J. Maury obtained P. 

 crassoramosa in Santo Domingo in what she designates zone D, which 

 is above the horizon of the Bowden marl. The geographic range of 

 the genus in the West Indies is, therefore, from the Antiguan 

 Oligocene to a horizon appreciably above that of the Bowden marl. 



POCILLOPORA ARNOLDI, new species. 



Plate*76, figs. 3, 3a, 36. 



The type, which is a fragment of a branch, is 28 mm. long, diameter 

 of lower end 6.5 by 12 mm., diameter of upper end 5.5 by 9 mm. 

 The cross section of the branch is strongly compressed, and one side 

 near and at a place of bifurcation is concave instead of being convex. 

 There are no verrucae. 



Calices slightly oblong, lesser diameter about 0.75 mm., longer 

 diameter, parallel to the axis of the branch, from 1 to 1.25 mm. 

 Cavities rather deep, about 0.5 mm., and steep-walled. Intercorallite 

 areas flattish, arched, or slightly crested in profile, of unequal width, 

 from 0.3 mm. to 1 mm. across. Coenenchymal surface granulo- 

 costulate, granulations fairly coarse. 



Septa rudimentary, occur as low, blunt-topped, perpendicular 

 ridges on the inside of the calicular walls. In some calices 12 of 

 these ridges may be distinguished. The bottom of the calice is flat 

 or very gently concave; no vestige of a columella could be found. 



Coenenchyma solid; corallite cavities solidly filled except a few 

 in the axis of the branch. 



Locality and geologic occurrence. — Canal Zone, station 6444, quarry 

 in the Emperador limestone, Empire, collected by Dr. Ralph Arnold, 

 whose name I take pleasure in attaching to this well-marked species. 



Type— No. 324782, U.S.N.M. 



Of the other five fossil species of Pocillopora known from the 



■Tertiary formation of the West Indies and Central America, the 



unnamed. species from Antigua, previously mentioned, is the most 



similar. The latter species is composed of small, more or less com- 



37149— 19— Bull. 103 11 



