80 ECHINODEKMATA OF THE ARCTIC SEA. 



north of the European and Asiatic continents, and is found in Behring's Straits. 

 Finisterre and Massachusetts are its most southern habitats. 



Solaster endeca has been found in Smith's Sound, Newfoundland, Iceland, and 

 in the English Channel ; and Brandt obtained it at Sitcha. The solitary species of 

 Lophaster is very Arctic, being found at Discovery Bay ; and it extends south in the 

 Gulf of Maine and at Bergen. 



Pteraster militaris has almost a corresponding, but slightly intermediate range ; 

 and the Ctenodiscus extends far over the north of the European continent, comes 

 only as far south as Maine in America, and reaches to lat. N. 70 30' off Greenland. 



It is evident that the grouping of these Asteroids is as if they were part of a 

 great Polar fauna, with no very great southern distribution. 



Of the Ophiuroidea, the new species Ophiopleura arctica belongs to a genus 

 characteristically Arctic. The Ophioglyphm, with the exception of 0. Stuwitzii, are 

 found very far to the north ; and their fellow Ophiuroidea at Discovery Bay and 

 Franklin-Pierce Bay are Ophiocten sericeum, Amphiura Holbcelli, and Ophiacantha 

 spinulosa. The range of these resembles that of the Asteroids to a certain extent ; 

 and they have curious structural affinities with even the forms from the Korean 

 Sea. The forms with a smaller northern area are the Ophioglyphce just alluded to 

 and Ophiopholis bellis. 



The Astrophyton ranges from 78 N. lat. up Smith's Sound to Cape Cod, and has 

 been found at Vadso, in Finmark. 



Antedon Eschrichtii and A. celtica are widely distributed northern forms ; and the 

 new species Antedon prolixa is from Discovery Bay. 



When these details are carefully considered, it becomes evident that each one of the 

 great groups of Echinodermata tells the same story regarding distribution. The fauna, 

 as a whole, is not an extension northwards of species from more temperate climates, 

 but is essentially circumpolar. The modifications in the character of the species are 

 probably due to variation produced by the changes of condition which necessarily occur 

 in different parts of any great area. 



