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. 
Measurements .—Apertura 
ha = 0.10 
Za = 0.18 
mm. 
mm. 
Apertura of ovicelled zooecium 
Zooecia 
Lz = 0.40-0.46 mm. 
lz = 0.34-0.36 mm. 
ha = 0.15 mm. 
la = 0.22 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 HIPPOTHOA (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, Mosdyr. Zoologica Danica (Danske Dyr), Hefte 9, p. 66, 
pi. 5, figs. 45-47. 
1896. Celleporella hyalina Nordgaard, Systemetisk fortegnelse over dei Norge hidtil observer de, 
arteraf marine polyzoa, I, Cheilostomata, Bergen’s Musuem Aarbogfor 1894-95, No. 2, p. 23. 
1900. Hippothoa hyalina Waters, Bryozoa from Franz-Josef Land, Journal Linnean Society London, 
vol. 18, p. 70, pi. 8, figs. 16-18. 
1900. Celleporella hyalina Nordgaard, Den Norske Nordnays-Expedition, Zoology no., vol. 17, 
p. 10. 
1902. Schizoporella hyalina Calvet, Bryozoaires marins de la region de Cette, Travaux de l’Institut 
Zoologie, University Montpellier, ser. 2, Memoire XI, p. 44. 
