326 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Genus HIPPOTHOA (Lamouroux, 1821) Hincks, 1880. 
Zoological bibliography. — 1877. Barrois, Recherches sur Tembryologie des Bryozoaires, Tra- 
vaux de l’lnstitut de zoologie, fasc. 1, p. 149, pi. 9. figs. 4, 16. — 1SS6. Jullien, Mission scien- 
tifique du Cap Horn, vol. 6, Zoology, p. 28, pi. 4, figs. 1-4. — 1900. Waters, Bryozoa from Franz 
Joseph Land, Journal Linnean Society, London, vol. 2S, p. 70, pi. 8, figs. 16-18. — 1900. Lev- 
insen, Morphological and systematic studies on the Cheilostomatous Bryozoa, p. 276, pi. 18, 
fig. 9. — 1904. Waters, Expedition Antarctique beige, Bryozoa, p. 53, pi 3, fig. S. 
Fig. 93. — Genus Hippothoa Lamouroux, 1821 (Hincks, 1880). 
A-I. Hippothoa hyalina Linnaeus, 1758. A. Portion of zoarium, X 25. B. Zoarium with 
ovicelled zooecia, X 36. (After Hincks, 1880.) C. Free larva, profile view, X 75. D. Oral 
face of larva, showing the singular structure of the stomach, X 75. E. Aboral face of larva, 
X 75, showing the simplicity of the structure of the terminal bud. (G-E after Barrois, 1909.) 
cd, digestive cavity ; ce, obscure portion of the body cavity included between the two branches of 
the stomach (=orifiee of the external sack) ; est, stomach; fl, flagellum; o, mouth of the gas- 
trula (=ciliated cleft); oc, oculiform points (=pigment spots); ph, pharpnx; pi, vibratile 
plume; rv, border of the terminal bud (=calotte). F. Operculum of male zooecium, X 85. G. 
Operculum of ordinary zooecium, X 85. H. Operculum of ovicelligerous zooecium, X 85. (F-H 
after Waters, 1900. ) I. A sagittal section through a gonozooecium. The ovicell is surrounded by 
a kenozooecium. ( After Levinsen, 1909.) J, K. Hippothoa bougainvillei, D’Orbigny, 1839. 
J. Young, uniserial zoarium with a spinous ancestrula and with a gonoecium without poly- 
pide, X 53. (J, K after Jullien, 188S.) K. Young zoarium exhibiting spinous ancestrula with 
opesium, X 53. 
The frontal of the zooecia is not porous. The operculum is compound. The 
aperture is provided with two much developed hinge-teeth and with a more or less 
