76 BULLETIN" 16 5, UNITED STATES NATIONAL MUSEUM 



Affinities. — It appears to us that the ovicell must have opened 

 into the peristomice, but we have not been able to make a thin section 

 confirming this. The species differs from B. lonsdalei in its smaller 

 micrometric dimensions and in the more salient, large triangular 

 avicularium. It differs from B. Idbiata Gabb and Horn, 1862, in 

 its larger micrometric dimensions and in the presence of a crown 

 of small avicularia around its peristomice. 



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



Cotypes.— U.S.N.M. No. 73938. 



BEISSELINA MORTONI, new species 



Plate 19, Figures 1-6 



1907. Porina quadrangularis (Gabb and Horn?) Ulrich and Bassler, in Weller, 

 Geol. Surv. New Jersey, Paleontology, vol. 4, p. 350, pi. 26, fig. 7 (not 8). 



Description. — The zoarium is free, bilamellar ; the fronds are nar- 

 row, subcylindrical or somewhat compressed, with subcircular or 

 elliptical cross section, bifurcated. The zooecia are indistinct, elon- 

 gated, arranged in quincunx, with 4 to 6 longitudinal rows to a 

 branch ; the frontal is covered by 6 avicularia with thick and slightly 

 granulose walls, visible exteriorly ; it bears an ascopore some distance 

 from the peristomice and opening into the interior of the zooecium 

 below the operculum. The apertura is buried at the bottom of an 

 oblique peristomie formed by the thickening of the frontal avicularia. 

 The peristomice is semielliptical, transverse, and bears an avicularian 

 mucron on its proximal lip. Each frontal is covered by six small 

 avicularia with small poriform orifice. The distal one is salient and 

 forms the avicularian mucron ; 2 others, laterally arranged, are sym- 

 metrically placed above the ascopore; 2 other lateral ones are sym- 

 metrically located below the ascopore and in the vicinity of the 

 peristomice of the adjacent zooecia; the last is proximal and opens 

 above the proximal peristomice. Sporadically the latter develops a 

 large triangular avicularium in which the beak is very salient above 

 the zoarial plane. 



Measurements. — 



„ \Lz= 0.34-0.6 mm. „ . ± . \hp = 0.07 mm. 



ZooeciumJ , Peristomice 7 r A11 



[fe=0.36 (!) mm. [^ = 0.11-0.13 mm. 



4 zooecia in 1 sq. mm. 



/Structure. — In longitudinal sections the structure is absolutely 

 analogous to that of other species of Beisselina, but the avicularian 

 walls are not so thick. The ascopore, often closed over by fossiliza- 

 tion, is here quite visible, and the large avicularium can be observed, 

 as in B. labiata Gabb and Horn, 1862. 



Variations. — The avicularium of the proximal umbo is the larger ; 

 it bears a pivot and is oriented distally or obliquely ; its beak is tri- 



