390 



THE INVERTEBRATA 



and by the freedom of some or all of the thoracic somites from the 

 carapace. The Eucarida do not possess a brood pouch and usually 

 have larval stages, their heart is a short chamber in the thorax, and 

 their carapace fuses with the dorsal side of each thoracic somite. 

 Independently in each of these two groups the caridoid facies has 

 been lost to various degrees, so that the members of each can be 

 roughly arranged in a series which, starting with prawn-like "schizo- 

 pods", ends in the Peracarida with the woodlice and in the Eucarida 

 with the crabs. 



Subclass LEPTOSTRACA 



Malacostraca with a large carapace provided with an adductor muscle 

 and not fused with any of the thoracic somites; stalked eyes; the 



Fig. 267. A female of Nebalia bipes. From Caiman, after Claus. a.' an- 

 tennule; a." antenna; ah} and ab.^ first and sixth abdominal limbs; add. ad- 

 ductor muscle of carapace; /. ramus of caudal furca; p. palp (endopodite) 

 of maxillule; r. rostrum; t. telson; i, 7, first and seventh abdominal somites. 



thoracic limbs all alike, without oostegites, biramous, and usually 

 foliaceous; seven abdominal somites, of which the last bears no ap- 

 pendages; and caudal rami on the telson. 



Nebalia (Fig. 267) is the commonest and typical genus of this 

 group. A^. bipes, the British species, may be found between tide- 

 marks, under stones, especially in spots which are foul with organic 

 remains. Nebalia has a rostrum, which is jointed to the head. The 

 antennae have no scale, while the antennules are unique in possessing 

 one. The carapace has an adductor in the region of the maxilla and 

 encloses the four anterior abdominal somites. The thorax is short. 



