BRYOZOAN FAUNA OF VINCENTOWN LIMESAND 69 



are united only by their distal extremity to the longitudinal median 

 axis and are decorated by a proximal pelma and distal pelmatidia 

 (or pelma). The apertural bar is wide, convex, of the same nature 

 as the costules. The aperture is suborbicular, somewhat elongated, 

 slightly narrowed laterally with a straight or concave proximal bor- 

 der ; the distal peristome is thin and salient, with four spines on the 

 little calcified zooecia, thick and smooth on the others. The ances- 

 trula is a, small ordinary zooecium. Each zooecium bears to the 

 right or to the left, a little below the transverse axis, a broad trian- 

 gular avicularium with denticles and with rounded beak, oriented 

 distally, often primoserial. 

 Measurements. — 



r, . \Lz= 0.65-0.8 mm. A , \ha= 0.15-0.17 mm. 

 Zooecmm| /s=0 ^ 045mm Apertura|^ =() ^ ^ ^ 



Variations. — Epicalcification is not active and rarely goes beyond 

 the zone of the costules; there is therefore no formation of a mural 

 rim limiting the costulated area. Nevertheless, it surrounds the distal 

 spines sufficiently to hide them and to thicken the distal peristome. 



The avicularium is often primoserial and oriented distally; when 

 it is not primoserial its orientation is more or less oblique. It is 

 often adjacent to the aperture of an adjacent zooecium, but it is 

 independent of it. Frequently the costules have two pelmata. 



The aperture is irregular in its dimensions ; it is more an opesium 

 in which the opercular valve covers only the distal portion. 



Affinities. — This beautiful species is quite distinct because of its 

 convex frontal, which is not outlined by a thick mural rim as in 

 Diacanthopora abbottii. It closely resembles Pelmatopora calceata 

 Lang, 1916, from the Senonian of England (Chatham) but differs 

 in its larger zooecial dimensions, in the presence of a proximal pelma 

 on the costules, and in its large and triangular avicularium. 



We believe that the two genera Diacanthopora and Pelmatopora 

 Lang, 1916, should be united, as the character that differentiates 

 them seems to us of little importance. In Diacanthopora the pelma 

 is proximal, while it is distal in Pelmatopora. On the American 

 species one can note that the distal pelmatidium is frequently trans- 

 formed into a true pelma. 



Occurrence. — Vincentown limesand : Rare at Vincentown, N.J. 



Cotypes.— U.S.N.M. No. 73909. 



DIACANTHOPORA MARGINATA Gabb and Horn, 1862 



Plate 20, Figuke S 



1862. Reptcscharipora marginata Gabb and Hokn, Journ. Acad. Nat. Sci. Phila- 

 delphia, ser. 2, vol. 5, p. 149, pi. 20, fig. 33. 



1922. Diacanthopora marginata Lang, Catalogue of the Cretaceous Bryozoa 

 in the British Museum, vol. 4, pt. 2, p. 232 (bibliography). 



