144 CKUSTACEA. 



Gills external, or wanting ; only three pairs 

 of members belonging to the mouth . . . Stomapoda. 



Gills fixed under the sides of the thorax, 

 and inclosed in special cavities ; six pairs of 

 members to the mouth ; five pairs of thoracic 

 feet Decapoda. 



Sitb-OrderL STOMAPODA. 



Feet usually seven pairs ; almost always pro- 

 vided with accessory appendages. Gills never 

 lodged in a special cavity; they are composed of 

 parallel filaments, which give forth other subor- 

 dinate filaments, which are again fringed in the 

 same manner. Abdomen greatly developed [in the 

 British species]. 



First feet very large and fanged ; next three 

 pairs short, and terminated by smaller fangs ; 

 last three pairs formed for swimming ; cara- 

 pace divided lengthwise Squilladte. 



All the feet of the same form, provided 

 with a process which makes them appear 

 double. Body compressed ; carapace con- 

 cealing the thorax Mysidce. 



Body consisting of a thin flat plate ; cara- 

 pace covering only a small part of the thorax ; 

 feet excessively long and slender Phgttosomadce. 



Family I. Squillam:. 



Squilla (Fabr.). Last three pairs of feet fur- 

 nished with a long style-shaped appendage ; fang 

 of first feet flattened and armed with strong teeth. 



S. mantis. 



Desmarestii. Fig. 270 ; i n. s. 



