42 BULLETIN 16 5, UNITED STATES NATIONAL MUSEUM 



a pivot; the beak is truncated, and the distal canalicule is open to 



allow the passage of the long mandibular seta. The ancestrula is a 



very small ordinary zooecium, the peristome of which bears only two 



small solid spines. 



Measurements. — 



„ . \Lz = 0.5 mm 1 (including . [k=0.09 mm. 



Zooecia 7 • n\ Apertura 7 AAO 



[fe = 0.3 mm jovicell). x [la =0.08 mm. 



33 zooecia in 4 sq. mm. 



Structure. — This species has the appearance of a Setosella, but 

 there are the important differences that the ovicell is not closed by 

 the operculum and the vibracula are replaced by the setiferous 

 avicularia. The presence of the long mandibular seta is unques- 

 tionable, as it is well proved by the truncated beak, which makes it 

 possible for the seta to emerge from the small distal canalicule. We 

 have always thought that such avicularia are tactile organs. Here 

 when the mandibular seta is completely open and pressed down, it 

 touches the operculum of the distal zooecium. The function of the 

 small perforated distal kenozooecium that surmounts many of the 

 zooecia is unknown. 



We have not observed true perforating opesiules; the place of 

 some of these is, however, sufficiently indicated to prove that they 

 must occur. They must have been very small, which explains their 

 disappearance in fossilization. 



The larvae must have been small and fragile and able only to fix 

 themselves with great difficulty. In spite of the great abundance 

 of ovicells, the species is in fact very rare. 



Without the ovicell, the zooecia measure only 0.35 to 0.4 mm in 

 length. 



Occurrence. — Vincentown limesand : Vincentown, N.J. (rare). 



Holotype.— U.S.N.M. No. 73903. 



Family COSCINOPLEURIDAE Canu, 1913 

 Genus COSCINOPLEURA Marsson, 1887 



COSCINOPLEURA DIGITATA Morton, 1834 



Plate 9, Figures 1-6 



1834. Eschara digitata Morton, Synopsis of the organic remains of the Cre- 

 taceous group of the United States, p. 79, pi. 13, fig. 8. 



1920. Coscino pleura digitata Canu and Bassler, U. S.Nat. Mus.Bull. 106, p. 275, 

 pi. 2, figs. 7-22 (bibliography). 



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

 row, dichotomously dividing on the same plane and forming a 

 flabelliform ensemble. The zoaria are distinct, separated by a deep 

 furrow, elongated, ogival in front, truncated behind, without mural 



