THE DECAPOD CRUSTACEA. 167 



antepenultimate segment, which morphologists call the wrist, 

 or carpopodite, is broken up into a number of joints, so that 

 it resembles a whip in appearance. 



The Esop prawn may be found not infrequently among 

 the " prawns " brought to market as food. 



Much smaller than Pandalus or Palcemon are the various 

 species of Hippolyte, which are common on our shores, but 

 not being large enough for use as food are not well known, 

 and have no common name. The commonest form is 

 H. varians, a beautiful little creature, about three-quarters 

 of an inch in length, and showing much variation in colour. 

 It is typically green, but among dark weed brown varieties 

 are common, and in pools lined with Red Algse the tint 

 may be distinctly reddish. In common with the other 

 members of its genus it has the following characters : Like 

 Pandalus, it has a hump-back, which is due to the same 

 cause ; the antennules generally resemble those of Pandalus, 

 but the thicker filament is much curved, and furnished with 

 numerous bristles ; both filaments are short. It differs from 

 Pandalus in the nature of the first pair of legs, for these 

 are short, equal, and distinctly chelate ; the second and re- 

 maining pairs closely resemble the corresponding appendages 

 in Pandalus. There is usually a well-developed rostrum, 

 and it is the condition of this structure which is chiefly 

 relied on in the distinction of species. In //. varians it is 

 straight, furnished above with one spine near the base, and 

 one near the apex, beneath it is sharply keeled, and bears 

 two spines. The inner filament of the antennules is only 

 very slightly curved. These characters should be sufficient 

 to distinguish this species, which is the only one which can 

 justly be described as common in the littoral zone of the 

 East Coast. On the West, however, and especially the 

 South-west, another species is sometimes extraordinarily 

 abundant. This is H. cranchii, which in certain parts of 

 the Devonshire coast seems to occur in every rock pool. 

 In life it is of a delicate green colour, with the appendages 

 ringed with pale blue ; but the green colour is very fugitive 

 after death. It reaches about the same length as the pre- 

 ceding species, but the greater breadth of the thorax gives 

 it a much more robust appearance. The rostrum is short, 

 furnished with three teeth above, besides the two in which 



