466 Prof. A 11 man on the Hydroida. 



brella of Medusa set with scattered thread-cells, and with its 

 transverse and vertical diameters nearly equal. Two longitu- 

 dinal furrows exist upon the concave surface of the umbrella; 

 they are situated exactly opposite to one another, each occupy- 

 ing the middle line of the interval between two neighbouring 

 radiating canals, and extending from the base of the manubrium 

 to the margin of the bell. Marginal tentacles of Medusa very 

 extensile, nodulated with clusters of thread-cells, which give 

 them a moniliform character when extended, one larger spheri- 

 cal cluster terminating the tentacle. Tentacular bulbs with 

 a distinct ocellus. Manubrium and tentacular bulbs deep 

 orange. 



Rooted to the bottom of rock-pools, near low-water mark, 

 Skelmorlie, Firth of Clyde. 



Syncoryne pulchella, though of humble habit, is yet conspi- 

 cuous by the bright orange-colour of its polypites and medusa- 

 buds. It is evidently nearly allied to the Syncoryne decipiens * 

 of Dujardin, with which indeed I was at first disposed to regard 

 it as identical. It agrees with it closely in the form of the 

 Medusa, and in the fact that all the gonophores are borne be- 

 hind the most posterior tentacula. Like the Medusa of the 

 present species, that of S. decipiens is described as being pro- 

 vided with linear longitudinal furrows on the concave surface of 

 the umbrella. In S. decipiens, however, each of the four inter- 

 vals which separate the radiating canals is stated to be occupied 

 by one of these furrows, while in the present species only two 

 of them are so occupied. The trophosome also of S. pulchella 

 differs from that of Dujardin's species in its simple habit, in the 

 more ovate form of the polypite, and in its more numerous 

 tentacles. 



With Syncoryne exirnia the present species closely agrees in 

 the form of the Medusa, though the trophosomes of the two 

 species are very different from one another. The Medusae, in- 

 deed, are scarcely distinguishable, except in the fact that the 

 subumbrellar furrows do not exist in those of S. eximia. 



The longitudinal furrows which we meet with on the concave 

 surface of the umbrella are probably fonned by a peculiar modi- 

 fication of the substance of the umbrella forming two fixed lines 

 of attachment for the circular contractile fibres. 



While examining the Medusse which had been thrown off 



» 

 * In a synopsis of the genera and species of the Tubularince, published 

 in the ' Annals of Natural History ' for May 1864, I regarded Syncoryne 

 decipiens, Dujard., as a synonym of S. Sarsii, Loven. Though in this view 

 I followed so excellent a zoophytologist as Mr. Alder (Catal. Zooph. of 

 Northumberland and Durham, Supplement, p. 3), I am now convinced 

 that the two species are distinct. 



