68 BULLETIN" 16 5, UNITED STATES NATIONAL MUSEUM 



Variations. — The special character of this species is that figured 

 by Gabb and Horn, 1862; the ovicelled zooecia are in appearance 

 longer than the others and measured 0.85 mm instead of 0.60 mm. 

 In reality it is the distal zooecium that is elongated by a distance 

 equal to that of the proximal ovicell; it develops a gymnocyst on 

 which the ovicell rests. 



The phenomenon of epicalcification, well figured although exag- 

 gerated by Gabb and Horn, is here quite apparent. It fills the 

 intervals between the cells, thus forming a thick mural rim. It com- 

 pletely surrounds the ovicell and forms around it a veritable crown. 

 Spines and avicularia are embedded in the calcareous material, 

 where even their traces are not always visible. 



On our specimens the number of costules is exactly that indi- 

 cated by Gabb and Horn's figure, which clearly confirms our deter- 

 mination. 



The intensity of the calcification is great, and we have been un- 

 able to verify the exact place of the avicularia. It seems to us, how- 

 ever, that their base is attached to the adjacent zooecia. This must 

 be verified on better specimens. 



Affinities. — The specific characters are well indicated on the dia- 

 grammatic figures of Gabb and Horn and are more apparent on 

 our own. Diacanthopora distans differs from D. abbottii in its 

 smaller micrometric measurements, in its smaller number of costules 

 (8 to 10 and not 14), and in a more intense epicalcification joining 

 all the zooecia together. The general structure is almost identical 

 with that of D. abbottii, and our remarks on the reconstruction of 

 the chitinized parts are the same. 



Gabb and Horn examined only a single specimen described as 

 follows : " Colony apparently in a tortuous anastomosing series of 

 plates, robust, cellules on both faces." The word " apparently " in- 

 dicates a slight doubt. Probably the colony examined was entirely 

 encrusting some bilamellar species as G oscinopleura digitata or Pli- 

 ophloea sagena. Our specimens are encrusting. 



Occurrence. — Vincentown limesand : Rare at Timber Creek, Vin- 

 centown, and near Blackwoodstown, N.J. 



Plesiotype.— U.S.N.M. No. 73908. 



DIACANTHOPORA CONVEXA, new species 



Plate 8, Figures 2. 3 



Description. — The zoarium encrusts Pliophloea sagena. The zoo- 

 ecia are distinct, separated by a deep furrow, elongated, oval, large, 

 swollen; the frontal is convex, surrounded by an individual epical- 

 cification, smooth, enlarged proximally, limiting an elliptical costu- 

 late area formed by 14 to 16 closely approximated costules ; the latter 



