No. 10.— Report on the Hydroida collected during the Exploration 
of the Gulf Stream and Gulf of Mexico by ALEXANDER AGASSIZ, 
1877-78. By S. F. CLARKE, Fellow of Johns Hopkins University. 
Or the twenty-six species of Hydroida collected by Mr. Agassiz in the 
Gulf Stream and Gulf of Mexico in 1877 — 78, one half are described as 
new among the forms from the collection of Mr. L. F. de Pourtalés re- 
ported on by Professor Allman ; * a similarity of fauna, which we would 
expect, owing to the close proximity and similar conditions of these 
regions. 
Two of the remaining thirteen are well known to science, one is unde- 
terminable, and ten are new. 
Fourteen genera are represented, one of which, Vematophorus, is new. 
The species upon which this new genus is founded is the most interesting 
form in the collection, as it possesses a set of structures which from 
their position and form render it not improbable that they represent 
rudimentary hydrothecw. The species are quite evenly divided among 
the comparatively large number of genera; only two of them being 
represented by more than two species, — Lafoéa with five, and Aglaophe- 
ma with four. 
The Plumularidan is the dominant type; eight species, nearly one 
third of the collection, belonging to this family. 
The following table contains a list of all the species in the collection, 
with the depths at which they were taken. 
HYDROIDA. 
GYMNOBLASTEA. 
Pennaria symmetrica sp. nov. Tubularia sp. 
Eudendrium distichum sp. nov. | 
CALYPTOBLASTEA. 
Campanularia coronato, sp. nov. Lafota robusta sp. nov. 101 fma. 
Obelia hyalina sp. nov. “ serrata sp. nov. 292 fms. 
“ marginata ALLMAN. “ venusta ۰ 
Lafota convallaria ALLMAN, 101-177 fms, | Halecium tenellum Hincrs, 36 fms: 
“ gracillima ALDER, 101 fms, Oryptolaria conferta ALLMAN, 101 fms. 
* Mem. Mus. Comp. Zool. Vol. V. No. 2. 1877. 
