﻿April, 1857.] 



ELLIOTT SOCIETY. 



139 



ogous with that of the Mediterranean, and that these two have so 

 distinct an appearance, on account of their short tentacula, that 

 Gegenbaur considered S. thelostyla a new type of Medusa. With 

 regard to the transparent tissue which clothes the bulb beneath, 

 and to which Gegenbaur seems to attach some weight, according 

 to my observations it exists not only in S. mirabilis and our own 

 species, but in other large-bulbed genera, as for instance Coryni- 

 tis where it is well marked. 



The largest specimen of this species yet found did not equal a 

 tenth of an inch in height, and though, as formerly remarked, not 

 entirely mature, I have yet found specimens in which the incipi- 

 ent sexual organs, on the sides of the digestive trunk, were easily 

 distinguishable, and I conclude that the greatest size attained by 

 the species can hardly be much more than one tenth of an inch 

 in vertical diameter. 



Specimens have been found as early as the beginning of June, 

 and as late as the latter part of September, but never have any 

 been taken during the winter. It may probably with safety be 

 set down as entirely a summer species. 



The Clavidse differ from the other Corynidse by their filiform ten- 

 tacula, which want the trrminal buttons of thread-cells. A similar 

 difference occurs between the oral tentacula of Tubularia and those 

 of Pennaria, yet Tubularia, when very young, agrees with Pen- 

 naria in this respect. An analogous difference takes place 

 between Sarsia and Corynitis, and I look upon it as only a slight 

 distinction. The fresh-water genus, Cordylophora, also agrees 

 with Clava in its tentacula, and I can scarcely doubt belongs to 

 this group, of which there is as yet no representative known in 

 our neighborhood. If I be correct in my conjecture, that the 

 fresh-water hydra is an Exostome, both the sub-orders will thus 

 have fresh-water representatives. 



2nd Group. VELELLIDJE. Eschscholtz. 

 The only free Medusa-form yet known in this group is Chryso- 

 mitra, which is characterized by a broad and unusually shallow 

 bell for the sub-order. Its digestive trunk is also short and 

 broad; its radiate tubes unusually numerous (16,) not branched, but 

 each originating in the upper portion of the digestive cavity, and 



