100 MR. E. S. RUSSELL ON A NEW HYDROID. [Feb. 6, 



at opening of umbrella -cavity. Exumbrella with a few nemato- 

 cysts scattered over it. Velum well developed. 



Manubrium, when extended, as long as umbrella-cavity, 

 cylindrical, and with narrowed end. 



Mouth simple, circular, with a ring of bead-like nematocysts 

 closely suri'ounding it. 



Four ocellar bulbs, ellipsoid : one of these is somewhat lai-ger 

 than the others. Radial canals four, simple. 



Dimensions. Length of bell 0'8 mm. ; breadth of bell 0*7 n>m. 



Colours. Manubrium tinged with yellow, but very faintly. 

 Ocellar bulbs golden yellow. 



The type specimen of Trichorhiza hrunnea was discovered on 

 June 29th, 1905, clinging to the tentacles of a specimen of 

 Corymorpha nutans Sars, dredged in 17 fath. at Ettrick Bay, Bute, 

 Firth of Clyde. The filiform hydrorhiza with its biunches was 

 intertwined among the tentacles of the Gorymorfhoj so as to be with 

 dilficulty unravelled from them. The IVichorhiza \\'iMi kept alive 

 for a day or two at the Millport Marine Biological Station, and 

 gave off on July 1st the medusoid which has been described. 

 It was usually to be seen half -retracted into its protective cup, 

 with the proximal tentacles much contracted, and the distal ones 

 looking like mere knobs. On the rare occasions on which it was 

 observed in an expanded condition, the tentacles of the outer 

 circle were seen to be held rather stifHy extended. 



Systematic. On account of its possession of two verticils of 

 tentacles, the proximal filiform and the distal capitate, Trichorhiza 

 is to be referred to the family Pennaridfe as constituted by 

 Allman (1). That family contained the following genera: — 

 Fennaina Goldfuss, Halocordyle Allman, Stauridium Dujardin, 

 Vorticlava Alder, Heterostephanus Allman, Acharadria Wiight, 

 and Acaulis Stimpson. 



Two other genera have sometimes been associated with the 

 Pennaridse, namely Blastothela Verrill, which is placed among the 

 PennaridjB by Delage et Herouai'd (3), and Tiarella Schulze, which 

 is referred to the same family by G. Herbert Fowler (4). But such 

 an assemblage of genera by no means makes up a homogeneous 

 family. K. 0. Schneider (6), in his critical revision of the 

 classification of Hydr-oids, has removed Stauridium to his amended 

 family of the Oorynidse. Tiarella, with its three rows of capitate 

 tentacles, has also been referred to this extended family of the 

 Coi-ynidje by Mme. Motz-Kossowska (5), who follows Schneidei''s 

 classification in the main. These two genera are rightly separated 

 from the other genera of Pennarida?, as they have little in common 

 with the Pennarian type. The seven which remain of the nine 

 genera mentioned above are all fairly closely allied to one anothei". 

 Halocordyle cei-tainly must l)e united with Fennaria, and we may 

 with Schneider also bring under Pennaria the genera Vorticlava, 

 Acharadria, Acaulis, and Heterostejihanus. Heterostephanus is 

 allied by its medusoid with the Corymorpha type. Blastothela too 



