340 EUDENDRIUM TENUE. 



Balliymefrical dislrihution. — Liuiiinanaii zone. 

 LocalUi). — Shetland Islands, G. J. A. 



This beautiful little Eudendrium is conspicuous by its large, bright-vermilion Iwdranths. It 

 occurred in considerable abundance on the " Out Skerries," and other exposed rocky islets of 

 Shetland, but was found only at the extreme edge of low spring tides, where it grew rooted to 

 the bottom of shallow rock pools. 



It was in the month of August that I met with it, but its season of greatest perfection 

 must have been then passed, for in none of the specimens could any trace of the gonosome be 

 found, while in many of them the hydranths themselves had disappeared from the summits of 

 the ranuili. 



*at* 9. Eudendrium tenue, Alex. Agassiz. 



Eudendrium tenue, — Aler. Agassiz, Illus. Catal. N. A. Acalepli*, p. KJO, fig. 220. 



TROPHOSOME. — Hydkocaulus slender, profusely and irregularly branched, 

 rising to the height of an inch and a half; perisaec annulated on the ultimate ramuli. 



GONOSOME. — Male GONOPnoKES in clusters upon the remains of atrophied 

 hydranths. 



Colour. — General colour light pinkish. 



Development of Gonosome. — June. 



Locality. — Massachusetts Bay, Mr. A. Agassiz. 



The diagnosis given above is derived from Mr. A. Agassiz's account of the species, aided 

 by the woodcut which accompanies his description, and which represents a male specimen of this 

 hydroid. He adds that the "species can at once be distinguished from the Eudendriurn dispar, 

 Agass., by its large clusters of medusae (sporosacs), while in the Eudendrium dispar the medusae- 

 buds are always somewhat scattered and never clustered together, as in Eudendrium tenue" 



I can scarcely understand this passage, as the male gonophores of Eudendrium dispar have 

 been described and figured by Professor Agassiz as forming a verticillar cluster round the base 

 of the hydranths, the female gonophores only being scattered — the usual condition in Eudendrium. 

 It would seem as if Mr. A. Agassiz had by some confusion compared the male gonophores of his 

 Eudendrium tenue with the female gonophores of Eudendrium dispar. 



Eudendrium tenue is evidently a form closely allied to the Eudendrium capillare of the 

 European side of the Atlantic. From this species, indeed, it would seem to differ chiefly in its 

 larger size, and in the fact (judging from Mr. A. Agassiz's figure) that the annulation of the 

 perisarc is not confined to the origin of the branches. There are slight differences, and I am by 

 no means convinced that the American hydroid is specifically distinct from the British. 



