No.412.] MORTH-AMERICAN INVERTEBRATES. 311 
Habitat: Usually found upon shells occupied by the hermit crab, but 
occasionally found upon fucus and occasionally also upon piles of docks. 
6. PoDOCORYNID. 
Colony very similar to that of the Hydractinide, as given above. 
Hydranths with single whorl of filiform tentacles surrounding base of the 
conical hypostome. 
Podocoryne carnea Sars. 
Trophosome : Hydranths slender, pinkish-white in color, and with filiform 
tentacles. 
Gonosome: Medusz borne in clusters about the hydranth just below 
the whorl of tentacles. When set free the medusa is of marked bell-shape, 
with definite velum, short manubrium of reddish color, four radial canals 
from the bases of which arise eight marginal tentacles. 
Habitat as in Hydractinia. 
Stylactis. 
Under this generic name Sigerfoos describes (American Naturalist, 
Vol. XXXIII) a hydroid having many points in common with the Podoco- 
rynidz, and it should probably be classed under this family. He has given 
to it the specific name Hooperi (cf. of. cit.). The following definitive 
characters have been given of it: 
Trophosome : Hydranths slender, with a length when fully expanded of 
about 3% of an inch. Tentacles in single whorl, filiform, and of variable 
number, eighteen to twenty-five. 
Gonosome: Gonophores borne upon specialized hydranths just below 
tentacles, and set free as meduse having four radial canals, eight tentacles 
Which are somewhat rudimentary, devoid of ocelli. Sexual products borne 
upon manubrium. Found on shells of Stygnuassa (Illyanassa) obsoleta. 
7. PENNARID&. 
Colony arborescent, pinnately branched, hydranths with two sets of 
tentacles, one proximal composed of ten to twelve, filiform, the other borne 
upon hypostome in two indefinite whorls, short and capitate. 
Pennaría tiarella McCrady. 
of origin. Hydranths large and flask-shaped, those terminating stem or 
branches appreciably larger than others. 
