94 



ZOOLOGY. 



like feet covered by the carajoace. The Nebalia li2)es (Figs. 

 115, lie) occurs aloug our coast. 



Order 6. Tlioracostraca (Shrimps, Lobsters, Crabs). — 

 This order inchides the Decapods, which have ten feet ar- 

 ranged in five pairs, the first pair enhirged, forming "nip- 

 pers;" the head and thorax are covered by a solid, thick 

 carapace; while the gills are attached to the hinder maxil- 

 lipedes and to the thoracic feet. The Decapods pass through 

 a metamorpliosis, the young being termed a zoea (Fig. 117). 



Fio. 118.— Common Hermit Crab. Natm'al size. After Morse, from Emerton. 



A curious creature is the hermit crab (Fig. 118, Evpa- 

 gurus Icrnliardus; see also Fig. 19), which, selecting ;m 

 empty shell, thrusts its soft hind-body into it, and uses it 

 as a protection — like Diogenes, carrying its house about 

 with it. Small hermit cj'abs are abundant in little shells iu 

 tidal pools along our coast. 



In the crabs (Fig. 110) the abdomen is very small and 

 folded to the under side of the head-thorax (cepludo-thorax). 

 Shrimps and crabs are sensitive to shocks and sounds. The 

 sense of touch resides in the hairs on the mouth-paits. 



