1512 CRUSTACEA. 



the temperate zone. With this addition, the numbers become one 

 hundred and forty-seven for the torrid zone, and one hundred and 

 eighty-nine for the extra- torrid. Sixteen of the cold-water species are 

 common to both the torrid and temperate zones, and twenty-nine occur 

 in the frigid zone, twenty-seven being peculiar to this zone. This is 

 strikingly in contrast with the Brachyura, of which two-thirds are 

 torrid species, and only five or six are known to extend into the cold 

 zone, of which but one is confined to it. 



XX. The Thalassinidea are mainly extra-torrid species. 



The Astacidea are divided between the warm and cold seas; the 

 Palinuridge and Scyllaridae being mostly of the former, and the Asta- 

 cidse almost exclusively of the latter. 



The Caridea spread largely over both zones ; but extensive groups 

 are extra-torrid, and some genera contain many frigid species. 



The Penseidea are mainly of the torrid zone. 



The exact ratios will be gathered from the preceding tables. 



XXI. The geographical relations of the subordinate groups are 

 shown in the following table. 



1. TEMPERATE AND FRIGID ZONE SECTION. 



.Species in the Species in the Tempe- 



Torrid zone. rate and Frigid zoues. 



Thalassinidea, .... 6 17 



Astacidea, ..... 24 50 



Astacidae, .... 1 46 



Scyllaridse, G. Arctvs, 1 



Palinuridae, G. Palinurus, 2 3 



Caridea. 



Crangonidse, ... 2 25 



Atyidae, G. Ephyra, ... 2 

 Palaemonidae. 



Alpheinae, G. Betaeus, 1 4 



Alope, . . 1 



Athanas, 1 



Hippolyte, 8 37 (19 frigid). 



Pandalinse, G. Pandalus, . . 4 (2 frigid). 



Palasmoninee, G. Cryphiops, . 1 



Pasiphseidae, G. Pasiphcea, 3 (1 frigid). 



Penaeidea, G. Eucopia, ... 1 (1 frigid). 



