AGASSIZ. NATUEAL HISTOEY OF THE UNITED STATES. 359 
Of the above genera nine only are really new; others which bear 
the name of Professor Agassiz having been formed by the snb-division 
or re-construction of older groups. Stomolophus has been already 
noticed, and is the only new genus of Discophorce here figured. 
TIimantostoma , Hidroticus, Rhyllorhiza , and Donacostoma are from 
the drawings and notes of Mr. W. W. Wood, taken in the Straits of 
Sunda and in the China Sea. Diplopilus , Couthouyia , Medora , and 
Zygonema are characterized from the manuscript and figures of 
Mr. J. P. Couthouy (assisted by Mr. J. Drayton), “ made during 
the exploring expedition under the command of Capt. Charles 
Wilkes,” and “ shortly to be published.” 
Throughout the Tabular View, Professor Agassiz, wherever 
possible, indicates the locality whence each species has been 
obtained, and, aided by such data, has drawn up the general survey 
of the geographical distribution of the Discophorce with which Part 
III. terminates. ITe has thus been led to infer “that the lowest 
Discophorce , the Lucernariadce, are the only ones which extend to the 
boreal Paunae, and that some genera, Aurelia and Pelagia for instance, 
are cosmopolites, while others, such as Cyancea proper, are peculiar 
to the northern hemisphere; others are tropical, such as Mastigias, 
Leptobrachia, Cephea, Rolyrhiza, Diplopilus and Plidroticus ; others 
still, Rhacopilus, Riacois , and Lobocrocis, are only to be found in the 
southern hemisphere, and many are quite local in their distribution.” 
Thus certain zoological provinces are characterized by their own forms 
even of these oceanic animals, and of such Professor Agassiz points 
out several. Influenced by his peculiar' views on the limitation of 
Paunae, he is, perhaps, somewhat prone to insist on the specific 
differences of Discophorce which other naturalists would unite and 
assign to wider areas, yet extensive districts still exist, the Disco¬ 
phorce of which are little, if at all known; such as the African coasts 
generally, the west coast of South America, and Japan. “ Among 
the low islands of the Pacific,” in the Indian ocean, and in the Ped 
Sea, Rhizostomece largely prevail; “ a striking contrast with the 
western coast of North and South America, where no Rhizostomece 
have yet been found.” To which we would add that while the 
pelagic LLaplostomece abound in tropical and sub-tropical seas they 
are almost wholly replaced in northern temperate shores by their fixed 
allies, the Lucernariadce, a group apparently wanting in tropical and 
southern latitudes. 
(To he continued.) 
