506 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



tive and fuse to it at the periphery of the columellar tangle. A 

 circle of fairly prominent septal granules distinguishable just within 

 and more or less attached to the wall. Pah small, but distinct and 

 relatively prominent, usually six in number, on the inner ends of 

 the two directives and before the lateral pairs. The synapticular 

 rings are very clearly distinguishable, apparently there are two, the 

 outer of irregular development. 



Columellar tangle well developed, with a small, erect central 

 tubercle. 



Locality and geologic occurrence. — Canal Zone, station 6016, quarry 

 in the Emperador limestone, Empire, collected by T. W. Vaughan 

 and D. F. MacDonald. 



Cotypes.—lXo. 325113, U.S.N.M. (3 specimens). 



PORITES (SYNARAEA) MACDONALDI, new species. 

 Plate 152, figs. 1, 2, 3, 3a, 4, 5, 5a. 



Corallum begins growth as an explanate plate with humps and 

 gibbosities on its upper surface, by continued growth the protuber- 

 ances rise into crests and compressed columiform lobes. The series 

 of illustrations on plate 152, figures 1, 2, 3, 4, 5, indicate the growth- 

 forms. 



Calices of moderate size, average about 1.5 mm. in diameter, occur 

 separately or in series, usually in series which range in length from 

 the diameter of two or three calices up to 18 mm. long with 11 calices. 

 Within the series, although the calicinal centers are clearly demarked, 

 the walls between adjacent calices are only slightly developed, 

 but the series are separated by distinct fairly continuous walls, 

 which are costate on top, or by coarsely reticular coenenchyma. In 

 many places the reticulum rises upward between calices, especially 

 at their corners, and forms papillae, similar to those in the papillate 

 species of Montipora. Such papillae may be single, with a basal 

 diameter of about 1 mm. and a height also of about 1 mm., or they 

 may fuse and form ridges as much as 7 mm. long and 1.5 mm. thick 

 at the base. The reticulum composing the papillae is of coarse 

 texture. 



As new calices are largely formed by fission, the septal arrangement 

 is not definitely schematic. Where it appears possible to recognize 

 a ventral directive, the laterals of the triplet are joined to it by 

 synapticulae at the periphery of the columellar tangle. There is a 

 ring of septal granules slightly detached from the wall, and corres- 

 ponding to it in position is an incomplete ring of synapticulae; 

 pari are present, but usually indefinite in development, in one calice 

 there appear to be eight; palar synapticulae indefinite. 



