UYDROZOA. 
Gce.l 11 
pillars; no special genital cavities, or rather a single large open infra- 
umbrellular cavity, with four inter-radial orifices ; central gastro- vascular 
cavity cruciform, the four branches ascending in the pillars and uniting 
in the centre of the sub-umbrella ; four genital ribbons, each formed of 
two bends, accompanying the four divisions of the central gastro -vascular 
cavity, on either side. 
I. Crambessidce, Arms elongate, undivided, without cirri, but provided, 
in the greater portion of their length, with oral frills ; eight marginal 
sense-organs, four radial, four inter-radial; four strongly developed genital 
valves, formed each of two rectangularly connected plates, protect the 
sub-umbrellular portions of the central cavity and of the genital organs 
{Catostylus^ Cramhessa). 
II. Rh. impervioe. Arm-pillars not isolated, united through the gastro- 
genital membrane, and forming in this manner four or eight genital 
cavities, which include the genital ribbons ; central body-cavity simple, 
undivided (^Rhizostomidce, Leptohrachidce^ Cepheidce, Polyclomidm^ Cas~ 
siopeidoR). 
Charyhdea periphjlla, Pdr. & Lea. ? ; Verrill, Tr. Conn. Ac. iii. p. 52. 
Abnormal forms and monstrosities of A ; Romanes (25), 
pis. XV. & xvi. 
Distribution, Local Lists, &c. 
On the zoo-geographical sub-division of the coast of Alaska and N.W. 
America, from Monterey to the Bering Sea, and on the character 
of the hydrozoan fauna of the A leu teo- Alaskan region, vide the intro- 
ductory notes by W. H. Ball and S. F. Clark to Clark’s paper (6). 
The occurrence of a species of Stephanoscyphus in the N. Atlantic (56° 11' 
lat. N., 37° 41' long. W., depth 1450 faths.) is announced in the report on 
the “ Valorous ” expedition (P. R. S. xxv. p. 223). S. J. Smith and 
O. Harger’s Report on the dredgings in the region of St. George’s Bank ; 
Tr. Conn. Ac. iii. pp. 1-57. The geographical and bathymetrical distribu- 
tion of the Plumulariidce is discussed by Kirchenpaubr (12), pp. 31-39. 
Genera and Species. 
Athecata (Gymnoblastica) and Gymnophthalmic Medus.®. 
Tiarella, g. n., Schulze (24). A solitary conical hydranth, with a short 
hypostome and three cycles of tentacles : an oral one, consisting of four 
or five short knobbed filaments, an intermediate of six, and a basal cycle 
of ten to fourteen more elongate, knobbed tentacles, provided near the 
tips with two external half-rolls, formed like the knobs of macro- and 
micro-cnidia ; hydranth continued inferiorly in a thin peduncle, the 
slightly dilated base of which forms the attachment. The hydrocaulus 
and the lower part of the hydranth are covered with a soft perisarc, 
of which the internal portion is partially condensed into a chitinous tube, 
protecting the lower part of the, in older specimens, almost evanescent 
1876. [vOL. XIII.] J 4 
