﻿432 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



Columella absent, or slightly developed and false. 



Locality and geologic occurrence. — Porto Rico, station 3191, 4 miles 

 west of Lares, in tlie Pepin o formation, collected by R. T. Hill. 



Type.—^o. 325231, U.S.N.M. 



It is possible that this species may ultimately be referred to the 

 genus Mycedium, to which it is very close. 



Genus PIRONASTRAEA D'Achiardi. 



1875. Pironastraca D'Achiardi, Corall. eocen. del Friuli, p. 7C, pi. 15, figs. 2a, 

 2b, 3a, 36, 3c, 3d. 



Type-syecies. — Pironastraca discoides D'Achiardi, from the Eocene 

 at Brazzano, Russitz, Cormons, and Rosazzo, Italy. 



The species described below as Pironastraca anguillensis is essen- 

 tially typical of the genus except that the basal epitheca is incom- 

 plete, occurrmg only as shreds in both the type-specimens from 

 Anguilla and in a specimen from Porto Rico, collected by !Mr. Bela 

 Hubbard, of the New York Academy of Sciences Porto Rico expedi- 

 tion. The columella of P. discoides, according to D'Achiardi, is a 

 single papilla. 



The following generic diagnosis is based on the two West Indian 

 species, P. anguillensis and P. antiguensis, descriptions of which are 

 subsequently given: 



Corallum more or less massive or formmg thick undulating plates 

 which expand from a subcentral basal attachment. Lower surface 

 mostly naked, a few epithecal shreds are present, finely costate; com- 

 mon wall synapticular in origin, but m places it is almost or quite 

 solid. Upper surface caliculate. 



Calices usually form subconcentric series, some are circumscribed. 

 In the series calicmal centers either distmct, or indistinct as in . 

 Pachyseris. Separated by rounded colliues, of equal slopes on laoth 

 the peripheral and proximal sides; no interseriul walls. 



Septa lamellate, v/ith few or no perforations; apparently some per- 

 forations near the columella, where the trabecular fusion is incom- 

 plete. Septal margins with obtuse, crowded dentations, which are 

 compressed transversely to the septal planes, and are more con- 

 spicuous around the axial fossa, where the calicinal centers are dis- 

 tinct, or along the bottom of the vaUey where the calicinal centers 

 are indistinct. Columella false, in places a few papillae may be 

 recognized. Septo-costae equal in size, directly confluent across the 

 coUines. 



Synapticulae greatly developed, small, crowded. 



Geologic occurrences. — Oligocene of Anguilla, Antigua, Cuba, and 

 Porto Rico. 



There seems to be only one genus of corals with which comparisons 

 need to be made. Milne Edwards and Haime^ proposed Oroseris^ for 



1 Polyp, foss. Terr. pal4oEoiques, p. 130, 1851. 



* A synonym of Comoseris D'Orbigny, according to Gregory, Juras. Cor. Cutch., pp. 154-156, 1900. 



