1498 CRUSTACEA. 



such are Micippa (5 species), Menaethius (9), Huenia (4), Parthenope 

 (3), Atergatis (17), Carpilius (13), all the Chlorodinae, including forty- 

 nine species, nearly all the Eriphinae, including eighteen species, Cha- 

 rybdis (15). At the same time, the species of the Torrid and Sub- 

 torrid Regions are in many cases equally numerous. Of species of 

 Charybdis, eleven species occur in each of these regions ; of the Car- 

 pilii, eleven are reported from the Subtorrid and but five from the 

 Torrid ; of the Menaethii, five are found in the Torrid Region, and six 

 in the Subtorrid, only two being common to both. These proportions 

 may be much varied by future investigations. Still it cannot fail to 

 be evident from a survey of the table, that the line between the 

 Torrid and Temperate zones is a natural zoological limit. A further 

 examination of the other subdivisions, will show, we believe, that all 

 of them are important. 



II. The Torrid species of Brachyura (Torrid and Subtorrid Regions) 

 greatly preponderate over those of the Temperate zone, the proportion 

 being above two to one. This fact is the subject of remarks by 

 Edwards, but with different conclusions from those which we would 

 deduce. 



III. The Frigid zone, as far as known, includes one species peculiar 

 to it, the Chionoecetes opilio. And Stenorhynclius phalangium, Hyas 

 o.raneus, Pyrtunm pusillus, Carcinus mcenas, and Cancer pagurus, are 

 all that are known to extend into it from the Temperate zone. Per- 

 haps the Cancer chirogonus from Kamtschatka (Telmessus cJiirogonus 

 of White) should be added. This may be in part evidence of the 

 little exploration hitherto made in the Frigid Seas. Yet, after the 

 investigations of Beechey, Fabricius, Kroyer, Rathke, and others, we 

 may be assured that the number of species is exceedingly small. 



IV. Within the Temperate zone, the species are most numerous in 

 the Warm Temperate, Temperate, and Subtemperate Regions; beyond 

 this, the number diminishes, being a quarter less in the Cold Tempe- 

 rate than in the Subtemperate, and half less in the Subfrigid. More- 

 over, in the last-mentioned region, seventeen out of the thirty-seven 

 species, or nearly one-half, occur in warmer temperate latitudes, only 

 twenty species being confined to the Region. 



V. In the Torrid zone, the species of the torrid region, amounting 

 to three hundred and forty-eight, exceed in number those of the 

 Subtorrid by only forty-two, although the Subtorrid region is not one- 

 third as great, both as to surface and extent of coast line. 



