OF THE ACALEPHiE OF NORTH AMERICA. , 303 



Let me first state, that the species found in Boston harbour belongs really to Brandt's 

 genus Staurophora ; for if there should be any doubt upon this jjoint, all further gen- 

 eralization might be perfectly unfounded. 



Staurophora is a genus of Uiscophorous Medusa?. My new species resembles so 

 much, in its general appearance, the common Medusa {^Aurelia aurita), that the first 

 specimen, which was brought to me by Mr. Huber, came in a jar of specimens of that 

 species, for which I had sent, and was brought up without being noticed. I, however, 

 afterward secured a great number of them, which were collected both by Mr. Charles 

 Girard and Mr. Huber, so that I have had ample opportunity to study fully the form and 

 structure of this animal, which is really an intermediate type between Eudora and 

 Berenice, having rather short marginal tentacles, similar, indeed very similar, to those 

 of Thaumantias ; and our species might easily be mistaken for something like Thuu- 

 mantias Pilosella, were it not for the want of central oral lobes or stomachal appendages, 

 instead of which we notice a simple cross extending nearly to the very margin of the 

 animal, and consisting of a membranous seam hanging downwards, in a manner almost 

 identical with that of Staurophora Mertensii, but differing, however, in its lobulation, the 

 margin of these membranous seams being only deeply undulated, but not pectinate. 



The motions of the species of Boston Bay agree also remarkably with the descrip- 

 tion given by Mertens of the species observed on the northwest coast of the American 

 continent. When progressing slowly, they advance like all Discophorous Medusje, by 

 alternately expanding and contracting the margin of their disks, and assuming suc- 

 cessively the appearance of a disk or that of a half-sphere. In this respect they 

 closely resemble the common Medusae. But when they contract more powerfully, 

 they assume a very different aspect. The angles of the cross become prominent, 

 and the intervening spaces are contracted in such a way as to give the whole disk 

 a quadrangular form, or even that of an emarginate four-rayed star, precisely as 

 Mertens has observed it in his species described by Brandt. The resemblance in 

 form, in movertient, in the position of the marginal tentacles, in the disposition of the 

 arms, as Brandt called the fringes forming the cross on the inner lower surface of 

 the disk, can, I trust, leave no doubt in the mind of any naturalist, that the Medusa 

 I am about to describe really belongs to the genus Staurophora of Brandt. 



It cannot be doubted, therefore, that whatever additional details of structure may 

 be observed in one will also sooner or later be discovered in the other ; and whatever 

 conclusion may be established respecting their systematic position will equally apply to 

 Eudora, Berenice, and Staurophora. 



Now, in the first place, I would mention that the disk presents a mass of gelatinous 



