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PROCEEDINGS OF THE 



[April, 1857. 



at Penzance Bay. On our American side of the Atlantic this 

 difference also exists, the only genus found on both sides of Cape 

 Cod being Clava,* so far as at present known. While from Long 

 Island Sound southward we find the genera Nemopsis, Pennaria 

 and Hydractinia, the two latter appearing to be represented by one 

 species from Point Judith on the coast of New Jersey to Charles- 

 ton Harbor. The mean annual temperature of Charleston Harbor 

 is about 66°, nearly the same as that of Sicily. Accordingly, leaving 

 out the genera peculiar to each place, we find the following, so 

 far as is at present known, common to the Harbors of Messina 

 and Charleston : Turritopsis, Tubularia, Zanclea, Sarsia (short 

 trunked), Porpita, Diphyes, among Endostomata. Among Exos- 

 tomata, besides Eucope proper and Eucheilota, which are repre- 

 sentative genera, we have Campanularia (proper,) Obelia^Liriope 

 and Cunina, common to the two. To these may be added Saphe- 

 nia, Pennaria, Eudoxia and Physalia, common to the Mediterra- 

 nean and to Charleston Harbor. Some of the species which repre- 

 sent these genera between the two regions are very similar to each 

 other. This is the case between Pennaria tiarella and P. Cavolinii 

 Sarsia turricula and Oceania thelostyla, Tubularia and Tubu- 

 laria cristata, Campanularia noliformis, and Eucope campanuliformis. 

 There appears to be, therefore, a natural analogy between the Faunas 

 of the Mediterranean and of our South Atlantic coast. And taking 

 the zone whose approximate boundaries are the isothermals of 50° 

 and 66°, we find that in America it includes the coast from Long 

 Island Sound to Charleston, while in Europe it stretches from the 

 southern coasts of Ireland and England, including its northward 

 prolongation, up the Irish channel, to the coast of Africa, the mean 

 annual temperature of Alexandria in Egypt being nearly that of 

 Charleston. In Europe the following genera appear to be com- 

 mon to the northern and sourthern parts of this zone : Oceania, 

 Turritopsis, Cladonema, Sarsia, Lizzia, Diphyes, (?) Agalmopsis, 

 Eucope, Thaumantias, Liriope, Aequorea, (?) Obelia, Campanula- 

 ria, Physalia; Velella and Porpita, probably have their northern- 

 most limit rather southward of the isothermal of 50°. 



In comparison, then, the Faunae of these zones, in the two 

 continents, saving their continental peculiarities, may be con- 



* As to Laoraedea and even Campanularia, as ordinarily circumscribed, we 

 cannot speak with an approach to certainty; there is every probability that in 

 each of these, not yet sufficiently investigated groups, two or more genera will be 

 ultimately distinguished, so soon as their medusas become sufficiently known. 



