GEOGRAPHICAL DISTRIBUTION. 15 



though ranging from the Mediterranean to the Arctic seas, does not 

 pass to the western side. Astrophiton Agassizii, on the other hand, is 

 a purely American species. So that the two sides of this region, 

 though agreeing in many things, are distinguished in others. Thus, 

 the genera Ophiothrix and Ophlocoina are quite wanting along the 

 northeastern shores of America. After passing Cape Cod, we find, to the 

 south, the genus Ophiura, Init only one species, the northern sj)ecies 

 of various genera disappearing, and a barren tract succeeds as far as 

 North Carolina, in which space I know of Ijut one Ophiuran, Oj^hiura 

 oUimcea, as a common resident. Once in the latitude of Charleston, 

 South Carolina, we meet a rich store of species, and encounter the gen- 

 era AmjjJuura, Ilemqjholis, and Ojjhlothrix in abundance; not, however, 

 the same species that occur in the Gulf of Mexico and among the Antilles, 

 in which narrow circle lives a distinct fauna, of surpassing richness ; — 

 there may be seen the myriads of Oiihlothrix Orstedii, OpMocoma echi- 

 nata, Ophiura cqjpressa, and Ojjhlopsila Ulisei ; while in the deeper 

 waters we have the curious forms of Asferochema and Asterojmrpa. 

 The development of the genus Ophiura is especially remarkable, and 

 quite characteristic. Passing the narrow isthmus, to the Pacific coast 

 of Central America, we light upon a distinct fliuna again, but one which 

 is a counterpart of that of the Gulf The same forms of Ophlothrix^ 

 OpMocoma, Ophionereis, and Ophiura. Following this coast to the 

 north, we in due time arrive at a temperate fauna, in the region of 

 Northern California. There, again, is a souvenir of the eastern coast ; 

 the characteristic Ophlojiholls, the Awjjhlura j^ugefana, and even an As- 

 trophyton, which recalls A. eucnemis. Striking now westward, and get- 

 ting to the Sandwich Islands, we are on the borders of what may be 

 termed the fauna of the great ocean, a fiuna presenting in its vast 

 range the greatest contrast to that of the Gulf of Mexico. This region 

 extends from the Red Sea and Zanzibar, on the west, to the Sandwich 

 Islands, on the east ; and from the Kingsmills group, on the south, to 

 the Loo-Choo Islands, on the north ! New forms here surprise us ; 

 Ophlojjeza replacing Ophiura, which is unknown ; then Ophlarachna, 

 Ophlomastlx, and Ophlarthrum ; while, on the other hand, the already 

 familiar Op)hlocoma and Ophiothrlx are abundant, though with new 

 features, as in Ophiothrlx longlpeda, or in Ophiocoma p)lca. Amp)hlura 

 is almost wanting, but one Ophionereis occurs. 



As to the fauni\3 of South Africa, Australia, and Southern South Amer- 

 ica, it is not well to speak, lest grave errors occur, from want of precise 

 knowledge. I will merely mention that I saw in the collection of Pro- 

 fessor Schmarda an Oj)hlof/J)/pha from New South Wales, — a very 

 interesting hint on the correspondence of this fauna with the northern 

 one. 



