190 PROCEEDINGS OF THE ACADEMY OF [1895. 



The main range of the genus Crangon comprises the cooler seas of 

 the northern hemisphere both in the Atlantic and Pacific. There 

 are three species showing a true circumpolar distribution: Or. 

 salebrosus, boreas and crangon. The two first named must be 

 regarded as true arctic animals, extending southward, it is true, in 

 more temperate climates, but preferring considerable depths, from 

 about 100 to 400 fathoms. Crangon crangon lives in very shal- 

 low water, extending not as far northward as Cr. salebrosus and 

 boreas, and a connection between the Atlantic and Pacific (Japanese) 

 localities is not known. Perhaps such a connection was only present 

 in former times, and this species can not be counted among 

 the circumpolar ones, but is a survival of a formerly more 

 extended distribution. The two varieties of Crangon crangon 

 described above prefer deeper water, 50 and 60 fathoms, and they 

 are restricted to one of the northern parts of the two great 

 oceans, affinis being found in the northern Pacific from Japan to 

 California, allmanni in northern Europe. Of the other species of 

 Crangon eight show a distribution similar to the two last varieties. 

 Five are litoral and restricted to the northern part of the Pacific, 

 especially Cr. sharpi and intermedins to the most northern parts 

 (Berings Sea and Alaska), Cr. angusticauda to Japan, and Cr. 

 munitus and franciscorum to the western coast of United States. 

 The latter replaces the typical Cr. crangon on this coast. A 

 sixth species, Or. agassizi, is found in the Atlantic near the eastern 

 coast of United States, and must be regarded as a true deep sea 

 animal, being recorded from about 200 to 900 fathoms. It is 

 replaced on the western side of America by a nearly allied abyssal 

 species, Cr. procax, 660-900 fathoms. On the western coast of 

 Central America is found a second abyssal species, Cr. atrox, between 

 600 and 700 fathoms, being closely related to the northern circum- 

 polar Or. salebrosus. The presence of these three abyssal species on 

 both sides of the American continent indicate a relation to the 

 northern circumpolar seas, according to their affinities with the north- 

 ern circumpolar species of the subgenus Sclerocrangon, but I do not 

 believe that this demonstrates the connection of the western and 

 eastern American seas in the tertiary period within the litoral, as 

 held to-day generally by authors. 



Finally there are two antarctic species: Or. capensis from the Cape 

 of Good Hope, and Or. antarcticus from South Georgia. The latter 



