NO. 2 OSBURN: eastern pacific BRYOZOA — CHEILOSTOMATA 301 



The primary ooecium is globular, smooth, 0.15 mm wide, but very 

 soon becomes covered by the pleurocyst of the succeeding zooecium, is 

 ribbed w^ith coarse costae like the frontal and bears a small rounded umbo 

 on the top. 



D'Orbigny described the species from Arica, Chile; Busk and Waters 

 recorded it from Cape Horn, and Jullien from Valparaiso, Chile. Waters' 

 Mucronella ? alvareziona (1887:57) from the Tertiary of New Zea- 

 land is certainly another species. As the synonymy indicates it has 

 been shifted about considerably. Busk (1854:72) evidently appreciated 

 its relationship to Umbonula: "Its nearest congener is Lepralia verru- 

 cosa." The nature of the aperture and operculum and the strongly 

 costate frontal with very large areolae definitely ally this species to 

 Umbonula, of which verrucosa Esper is the genotype. 



Hancock Station 394-35, Lobos de Afuera Islands, Peru, 6°56'04''S, 

 80°43'00''W, at 12 fms. 



Genus HIPPOPLEURIFERA Canu and Bassler, 1927 



"The ovicell is hyperstomial and is not closed by the operculum. 

 The frontal bears at least a double row of areolar pores separated by 

 radial costules. The cardelles are small. There are spines on the peristome 

 and zooecial avicularia in which the beak is always oriented toward the 

 top of the zooecia" (Canu and Bassler, 1927:7). Genotype, Eschara 

 j-e^^zffc^i Milne-Edwards, 1838. 



Canu and Bassler (1929:326) compared it with Umbonula, and 

 Hastings (1949a: 521-528) has since made a critical study of the 

 genus and arrived at the conclusion that it should be associated in the 

 same family, Umbonulidae. 



The essential difference between the genera lies in the complete 

 absence of cardelles in Umbonula; there are well-developed oral spines 

 in Hippopleurifera while none have hitherto been observed in Umbonula. 

 However, this latter distinction has disappeared on the discovery by 

 the writer of minute spines on young marginal zooecia of Umbonula 

 patens (Smitt). 



Hippopleurifera mucronata (Smitt), 1873 

 Plate 35, figs. 7-8 ; Plate 36, fig. 1 



Hippothoa mucronata Smitt, 1873:45. 

 Hippomenella rubra Canu and Bassler, 1928:108. 

 Hippomenella mucronata, Osburn, 1947 :33. 



