No. 10. — Report on the Hydroida collected during the Exploration 

 of tlie Gulf Stream and Gulf of Mexico ly Alexander Agassiz, 

 1877-78. By S. F. Clarke, Fellmo of Johns Hopkins Universiiy. 



Of 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 fonns from the collection of Mr. L. F. de Pourtales 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, Nematophorus, 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 hydrothecae. The species are quite evenly divided among 

 the comparatively large number of genera ; only two of them being 

 represented by more than two species, — Lafoea with five, and Aglaophe- 

 nia with four. 



The Plurmdaridan 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. i Tubularia sp. 



Eudendrium distichum sp. nov. | 



CALYPTOBLASTEA. 



Campanularia corcmata sp. nov. 

 Obelia hyalina sp. nov. 



" marginata Allman. 

 Lafoea convallariaAiSLTAk.'S, 101-17/ fins. 

 " gracillima AiM-EK, 101 fms. 



Lafoea robusla sp. nov. 101 fms. 



" serrata sp. nov. 292 fms. 



" venusta Allman. 

 Halecium tcnellum Hincks, 36 fms. 

 Cryptolaria c&nferta Allman, 101 fms. 



* Mem. Mus. Comp. Zool. Vol. V. No. 2. 1877. 



