No. 413.] MORTH-AMERICAN INVERTEBRATES. 389 
3, Hf. tenellum Hincks. 
Trophosome: Colony minute, extremely delicate; stems slender, often 
strongly annulated, branching irregularly. Hydrothece funnel-shaped and 
with everted margins. 
Gonosome : Gonangia ovate, pedicellate. 
4, Hf. muricatum Ell. and Sol. 
Trophosome: Colony stout, dendritic, profusely branched, and with 
joint-like divisions, alternately from below which the hydrothecz arise. 
Gonosome : Gonangia ovate, borne on short pedicels, roughly marked 
with linear ridges of spinous processes. 
Eastport, Me. (Verrill). 
SERTULARID&. 
Synopsis of Genera. 
SERTULARIA. Colony plant-like, stems more or less branching, jointed, 
attached by creeping hydrorhiza. Hydrothece in double rows, strictly 
opposite, usually devoid of operculum. Gonangia with plain margins. 
SERTULARELLA. Colony resembling somewhat the former. Hydro- 
thece in double rows, but distinctly alternate, with toothed margins and 
with an operculum composed of several pieces. Gonangia strongly annu- 
lated throughout, slightly dissimilar in the two sexes. 
DipHAsta. Colony more or less branching, stem jointed, hydrothece 
opposite, a pair to each internode and often with a valve-like operculum. 
Gonangia scattered, differing in shape in the two sexes, those of female 
large, often divided into segments above, male smaller and with central 
tubular aperture. 
THUIARIA. Stem somewhat plant-like, jointed ; hydrothece in double 
series sub-opposite, but deeply immersed in the substance of stem and 
branches. 
HYDRALLMANIA. Stems flexuous or somewhat spirally inclined. Hydro- 
thece alternate, placed on front of branches, and curved alternately to 
right and left. 
Sertularia Linn. 
Generic characters given above. 
1, S. pumila Linn. (Fic. 26), 
Trophosome: Stems straight or slightly curved, simple or branched ; 
branches opposite ; both stem and branches divided into short internodes, 
each bearing a pair of hydrothece, the latter opposite, tubular, and some- 
what contracted toward the aperture, which faces outward and is more or 
less cleft or notched. 
