1524 CRUSTACEA. 



Tetradecapoda. Among the former, there are the thorny Lithodes, 

 the numerous Maioids armed with spines, the Acanthodes; while the 

 Cancroids and Grapsoids of the tropics are usually very smooth and 

 often polished species. There are the spinous boreal Crangons, the 

 species of which genus in the warmer seas are without spines. Among 

 the Tetradecapods, the boreal Iphimedise are often spinous or crested; 

 Acanthonotus and Dulichia are spinous genera. The same tendency 

 is seen in the third pair of caudal stylets in some cold-water Gammari, 

 which have the branches spinulous instead of furnished with a few 

 minute hairs like those of the tropics. 



There are also some spinous Crustacea in the tropics, as the Pali- 

 nuridae and species of Stenopus. Such facts, however, do not lead to 

 any modification of the previous remark ; for the tendency observed 

 is still a fact as regards the several genera mentioned. 



ENTOMOSTKACA. 



The Entomostraca have been little studied out of the Temperate 

 zone, if we except the results of the author's labours. The described 

 species of most of the families are, therefore, almost exclusively from 

 the temperate regions, and we know little of the corresponding species 

 or groups in the warmer seas. The following table presents the 

 number of known species of the torrid and extra-torrid zones, omit- 

 ting the Lernaeoids : 



TABLE IV. 



Torrid zone. Extra-torrid tone. 

 LOPHYROPODA. 



Cyclopoidea, .... 120 76 



Daphnioidea, ... 5 46 



Cyproidea, .... 13 61 



PHYLLOPODA. 



Artemioidea, .... 10 



Apodoidea, . 3 



Limnadioidea, .... 2 2 



PCECILOPODA. 



Ergasiloidea, .... 1 4 



Caligoidea, .... 16 33 



Were we to leave out of view the researches of the author, the 

 number of species and the proportion for the Cyclopoidea, instead of 

 120 to 76, would be about 3 : 50, thus not only reversing the ratio, 



