290 MANUAL OF NATURAL HISTORY. 



hind-legs flattened, ending in a large lamel- 

 late joint for natation. 



20. Family. — False Frog-Crabs (Hippidae) Cara- 



pace transversely oval, convex, prolonged on 

 each side into a lamella which covers bases of 

 legs j antennae very long ; foot-jaws with 

 last joint very much developed ; fore-legs 

 monodactyle or sub-cheliform, hind-legs end- 

 ing in a lamellar joint for digging in the 

 sand, fifth pair filiform. 



21. Family. — Hermit-Grabs (Paguridae). Carapace 



triangular ; outer antennae with a spiniform 

 piece below second joint ; outer foot-jaws pe- 

 diform ; fore-legs unequal, ending in a large 

 hand with short strong pincers, fourth pair 

 of legs short, didactyle, raised above the 

 others, fifth pair very short, on the sides of 

 the body, ending in a pincer more or less 

 well-formed ; abdomen soft, usually protected 

 by an adventitious shell. 



22. Family. — Lobster-Grabs (Porcellanidae). Cara- 



pace sub-circular, depressed, front produced 

 below insertion of inner antennae ; eyes small ; 

 outer antennae very long ; outer foot-jaws 

 very large, their second joint with a lamellar 

 dilatation on the inner side ; fore-legs large 

 and flattened, hind-pair slender and didac- 

 tyle ; abdomen large, ending in a laminated fin. 



III. SUB-ORDER. — Long-Tailed Decapods (Macroura). 

 Abdomen greatly developed, serving for natation, 



