﻿GEOGRAPHICAL DISTRIBUTION. ^5 



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

 pass to the western side. Astrojihyton 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 Oiilviothrix and Ophiocoma are quite wanting along the 

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

 south, the genus Ojilimra, but only one species, the northern species 

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

 North Carolina, in which space I know of but one Ophiuran, Ophiura 

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

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

 era Amphkira, Hem'qihoUs, and Op)hiothrix 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 Ojihiothrix Orstedii, Ophiocoma echi- 

 nata, Ophiura appressa, and Ophiopsila Eiisei ; while in the deeper 

 waters we have the curious forms of Asterochema and AsterojJorjxt. 

 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 fauna again, but one which 

 is a counterpart of that of the Gulf The same forms of Op)hiothrix, 

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

 north, Ave 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 Ophiopholis, the Amphiura pugetana, 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 fauna 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 ; 

 Ophiopeza replacing Ophiura, which is unknown ; then Ophiarachna, 

 Ophiomastix, and Ophiarthrum ; while, on the other hand, the already 

 familiar Ophiocoma and Ophiothrix are abundant, though with new 

 features, as in Ophiothrix longipieda, or in Ophiocoma p)ica. Amphiura 

 is almost wanting, but one Oj^hionereis occurs. 



As to the fiiuuEB 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 Ophioglypha from New South Wales, — a very 

 interesting hint on the correspondence of this fauna with the northern 



