142 BULLETIN 125, UNITED STATES NATIONAL MUSEUM. 



Genus EURYSTOMELLA Levinsen, 1909. 



1909. Eurystomella Levinsen, Morphological and systematic studies on the cheilostomatous 

 Bryozoa, p. 314. 

 Characters same as for the family. The operculum closes the ovicell. 



EURYSTOMELLA BILABIATA Hincks, 1884. 



Plate 37, fig. 6. 

 1884. Lepralia bilabiata Hincks, Polyzoa Queen Charlotte Islands, Annals and Magazine Natural 



History, ser. 5, vol. 13, p. 49, pi. 3, fig. 1. 

 1908. Lepralia bilabiata Robertson, The incrusting Cheilostomatous Bryozoa of the West coast of 

 North America, University of California Publications, Zoology, vol. 4, no. 5, p. 298, pi. 21, 

 figs. 61-64. 

 Our fossil specimens of this species are mediocre and do not permit us to add 

 any useful contribution to the laiowledge of this remarkable species. We therefore 

 have no modifications to add to Levinsen's description. 



Occurrence. — Pleistocene: Dead Man's Island, off San l^edro, California (rare). 

 Habitat. — Pacific: California and Queen Charlotte Islands. 

 Plesiotype.—Ca,t. No. 6SG.35, U.S.N.M. 



Family STOMACHETOSELLIDAE Canu and Bassler, 1917. 



Genus LEIOSELLA Canu and Bassler, 1917. 



(For description see Bulletin 106, U. S. National Museum, p. 448.) 



LEIOSELLA EDAX, new species. 



Plate 22, figs. 1-6. 



Description. — The zoarium is free, unilamellar, often tubular; it was attached 



to the delicate radicells of algae. The zooecia are indistinct. The peristomice is 



very large, elongate, provided with a large rimulc spiramen; the peristomie is 



deep; the apertura (in the interior) is semilimar with a concave proximal border. 



The oviceU is placed in the peristomie; it is widely open above the operculum; it 



bears a circular, very fragile frontal area. Around the peristomice there are three 



or four small, round, salient avicularia, with two denticles for pivot; they are 



sometimes transformed into large avicularia with spatulate mandibles. Another 



avicularium opens into the peristomie. 



f7io = 0.1.5 mm. Zooecia[L2 = 0.40 mm. 



Measurements. — Aperturai, „\'^^ ' ,. • J, "„'„„„ ' 



^ Ua =0.125 mm. (mterior)!^^ =0.30-0.35 mm. 



Affinities. — The aspect of this species is quite variable and depends solely on 

 the number and development of the frontal avicularia. It appears very greedy for 

 oxygen, a fact which is supported by the great thickness of its frontal wall and the 

 activity of the calcareous secretion. Sometimes two small avicidaria are replaced 

 by a much larger one with large spatulate mandible. 



The peristomie is the real seat of life of this species. An avicularum (visible 

 from the interior) opens into the lateral portion. The distal portion is reserved for 

 the ovicell. Finally, the pseudo-rinaule spiramen in the proximal portion is the 

 orifice of the hydrostatic system. It is probable that the female polypide disap- 

 pears by histolysis at the moment of the development of the embryos and the 

 escape of the larva. 



Occurrence.— Lower Miocene (Chipola marl) : Chipola River, Calhomi County, 

 Florida (rare). 



Cotypes.—C&t. No. 68636, U.S.N.M. 



