196 PROCEEDINGS OF THE ACADEMY OF [1895. 



America. Characteristic of the first is Crangon angusticanda; Pon- 

 tophilus bidentatus ; of the second, Crangon sharpi, C. intermedins, 

 Nectocrangon alaskensis ; of the third, Crangon munitus, C. francis- 

 corum, Paracrangon echinatus. 19 In the Atlantic, we have species 

 peculiar to the European coasts: Crangon crangon allmanni, Ponto- 

 philus echinatus, P. spinosus, P. pattersoni, P. sculptus, P. bispinosus, 

 P. trispinosus, P. fasciatus, P. negleetus, and one peculiar to the east 

 coast of America: Pontophilus breviorostris. 



Accordingly, within the limits of the arctic region we can dis- 

 tinguish three sub-regions: 1. The arctic-circumpolar ; 2. the Atlantic- 

 boreal] 3. the Pacific-boreal. The two latter are divided into local 

 faunas, the Atlantic into the northern European and the fauna of the 

 east coast of United States ; the Pacific into the local faunas of the 

 Berings Sea, of Japan, and of the west coast of North America. 



The arctic litoral region is the centre of origin of the family of 

 Crangonidae, and the centre of its development. The geographical 

 distribution of the species not living within the arctic litoral may 

 be characterized and classified as follows: 



1. Survivors of a more cosmopolitan distribution in the tropics of 

 Indo-Malaysia: Pontocaris propensalata, P. pennaia. 



2. Immigrants into the litoral of warmer seas from the northern 

 litoral : Pontophilus cataphractus , P. carinicauda. 



3. Immigrants into the deep sea. 



a. Localized species. 20 North Atlantic: Crangon agassizi, 200-900 

 fath., Sabinea hystrix, 400-900 fath.; Indo-Malaysia: Pontophilus 

 bengalensis, 107-270 fath., P. andamanensis, 180-i'20 fath., P. 

 junceus, 250 fath., Prionocrangon ommatosteres , 200-400 fath.: off 

 Australia: Pontophilus profundus, 2600 fath.; off western coast of 

 Central America: Crangon atrox, 600-700 fath., Cr. procax, 600- 

 900 fath., Pontophilus occidentalis, 900-2200 fath., Paracrangon 

 areolatus, 670-680 fath. 

 b. Widely distributed abyssal species: Pontophilus gracilis, 200- 

 700 fath., Pontophilus abyssi, 1700-2200 fath., Pontophilus chat- 

 lengeri, 1100-2700 fath. 



4. Immigrants into the litoral of the antarctic region. 



Crangon antárcticas , Cr. capensis, Pontophilus auslralis, P. inter- 

 medins. 



19 Paracrangon echinatus is perhaps an abyssal species, judging from the 

 depth recorded for Paracrangon areolatus. 



20 Some of these species may be more widely distributed. 



