92 BULLETIN 125, UNITED STATES NATIONAL MUSEUM. 



Genus METRACOLPOSA Canu and Bassler, 1917. 



(For description, see Bulletin 106, U. S. National Museum, p. 304.) 

 METRACOLPOSA MUCRONATA, new species. 



Plate 35, fig. 4. 



Description: — The zoarium incrusts shells. The zooecia are large, elongate, 

 elliptical, distinct, convex, separated by a deep furrow. The costules, numbering 

 10 to 12, are wide, robust, convex, and bear some lumen pores; the lacunae are 4 in 

 number and are small and orbicular. The apertura is oblique, elliptical, transverse; 

 its proximal border bears a bifid, salient mucro. The ovicell is large, salient, con- 

 vex; keeled, sunken in the distal zooecium; it opens in front of the mucro and can 

 not be closed by the operculum. 



f;ta = 0.10mm. ^ . [is = 0.40-0.46 mm. 



Measurements.-Apevtm^ll^^^^^ ^^ 2°°"^^^ Z2 = 0..34-0.36 mm. 



. . „ , . (^a = 0.15mm. 



Apertura of ovicelled zooecmm , _ „„ 

 ^ [ta = 0.^^ mm. 



Affinities. — The genus Metracolposa was discovered in the American Eocene 

 formations, where it is widely represented by vigorous, bilamellar species. Its 

 presence in the zone of the Pacific seems to indicate a great geographic extension in 

 geologic time. Its presence even in the recent seas is quite probable. We should 

 recall that the mucro of the Cheilostomatous zooecia is an apparatus of protection 

 for the passage of the eggs. 



Occurrence. — Pleistocene: Santa Barbara, California (rare). 



Holotype.— Cat. No. 68530, U.S.N.M. 



Family HIPPOTHOIDAE Levinsen, 1909. 



Genus fflPPOTHOA (Lamouroux, 1821) Hincks, 1880. 



(For description, see Bulletin 106, U. S. National Museum, p. 326.) 



HIPPOTHOA HYALINA Linnaeus, 1768. 



Plate 35, figs. 5-8. 



1768. Cellepora hyalina Linnaeus, Systema Naturae, ed. 12, p. 1286. 



1859. Lepralia hyalina Busk, Monograph Fossil Polyzoa of the Crag, Publications Paleontographical 



Society, London, vol. 14, p. 52, pi. 5, fig. 1. 

 1880. Schizoporella hyalina Hincks, British Marine Polyzoa, p. 271, pi. 18, figs. 8-10. 

 1889. Schizoporella hyalina Jelly, A synonymic Catalogue Recent Marine Bryozoa, p. 227 (biblio- 

 graphy). 

 1894. Schizoporella hyalina Levinsen, MosdjT. Zoologica Danica (Danske Djt), Ilefte 9, p. 66, 



pi. 5, figs. 45-47. 

 1896. C«HcporeHa Aj/aMna NoRDGAARD, Systemetisk f ortegnelse over dei Norge hidtil observer de, 



arteraf marine polyzoa, I, Cheilostomata, Bergen's MusuemAarbog for 1894-95, No. 2, p. 23. 

 1900. Bippothoa hyalina Waters, Bryozoa from Franz-Josef Land, Journal Linnean Society London, 



vol. 18, p. 70, pi. 8, figs. 16-18. 

 1900. Celleporella hyalina Nordoaard, Don Norske Nordnaya-Expedition, Zoology no., vol. 17, 



p. 10. 

 1902. Schizoporella hyalina Calvet, Bryozoairos marins de la region de Cette, Travaux de I'Institut 



Zoologie, University Montpellier, ser. 2, Memoire XI, p. 44. 



