78 BULLETIN" 16 5, UNITED STATES NATIONAL MUSEUM 



spatulate or semielliptic ; its beak is rounded and salient above the 

 zoarial plane. 



Measurements. — 



„ . x . [hp = 0.13-0.16 mm. „ . \Lz = 0.72-0.75 mm. 

 Penstomice \ l __ n , nia Zooecium _ n o«/ 9 \ 



[lp = 0.13-0.16 mm. 1/2 = 0.36 (?) mm. 



18 zooecia in 4 sq. mm. 



Structure. — The structure is identical with that of B. Idbiata Gabb 

 and Horn, 1862, as confirmed by sections. Around each peristomice 

 there is a crown of five small salient avicularia, which give to the 

 ensemble the aspect of Porina coronata Reuss, 1869. This arrange- 

 ment is frequent in many of the species of the Acroporidae and is 

 not peculiar to Acropora Reuss, 1869. A remarkable fact is that 

 the ascopore opens always in the immediate vicinity of the large 

 avicularium and even perforates its cryptocyst; the mandible, in 

 opening, touches the ascopore and closes it. 



The hydrostatic function of this large avicularium here appears 

 perfectly evident, namely, its mandible closes in order to open the 

 ascopore, thus permitting the water to enter the compensatrix, open- 

 ing the operculum and permitting the tentacles to emerge. But we 

 do not understand why the other cells are not likewise equipped. 



Affinities. — In spite of the exterior aspect this species does not 

 belong to Acropora, for its zoarial walls are formed of avicularia 

 and not of tubes, and the large avicularium is proximal and not 

 placed between the ascopore and the peristomice. The latter char- 

 acters are essentially those of the genus Beisselina Canu, 1918. We 

 cannot retain the specific name coronata because there already 

 exists Beisselina coronata Hagenow, 1851, from the Maastrichtian of 

 Limbourg, so we propose the new designation in honor of William 

 Lonsdale, who, among other activities, was a pioneer student of 

 American post-Paleozoic Bryozoa. 



Biology. — Canu, 1918, believed that the numerous species of Beis- 

 selina in the Danian and Maastrichtian epochs indicated agitated 

 waters and strong currents. This was an error, as the avicularia on 

 the contrary multiply their number and their size in deep and calm 

 waters. In order to construct such large colonies these small ani- 

 mals had need of considerable quantities of nourishment (diatoms). 

 In order to obtain such food it is absolutely necessary that the water 

 be constantly renewed, which is precisely the function of the 

 numerous avicularia. We suppose also that the large avicularia 

 arranged in linear series had the mandibles for a simultaneous move- 

 ment and destined to create a slight current over the zoarial surface. 



Occurrence. — Vincentown limesand: Rare at Vincentown and 

 near Blackwoodstown, N.J. 



Holotype.— U.S.N M. No. 52613. 



