94 
200L0Gr. 
like feet covered by the carapace. The Nehalia hipes (Figs. 
115, 116) occurs along our coast. 
Ordei' 6. Tlioracostraca (Shrimps, Lobsters, Crabs). — 
This order includes the Decapods, which have ten feet ar- 
ranged in five pairs, the first pair enhiiged, forming nip- 
pers;" the head and thorax are covered by a solid, thick 
carapace; while the gills are attached lo the hinder maxil- 
lipedes and to the thoracic feet. The Decapods pass through 
a metamorpliosis, the young being termed a zoea (Fig. ll*?). 
Fig. 118.— Common Hermit Crab. Natural size. After Morse, from Emerton. 
A curious creature is the hermit crab (Fig. 118, Eupa- 
gurus lernhardus; see also Fig. 19), which, selecting an 
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 crabs are abundant in little shells in 
tidal pools along our coast. 
In the crabs (Fig. 119) the abdomen is very small and 
folded to the under side of the head-thorax (cephalo-thorax). 
Shrimps and crabs are sensitive to shocks and sounds. The 
sense of touch resides in the hairs on the mouth-parts. 
