CEUSTACEA OF ISHEW ZEALAND. 189 



margin of the head, which, however, is nearly straight and is not hollowed out for the 

 reception of the mandible as described by Sars [91, j). 94] in Asellus aquaiicus. Below 

 the base of the lower antennae arises the 3-jointed palp, which extends forward beneath 

 the antennae, its third joint being usually bent sharply inward, nearly at right angles to 

 the second. Prom this point the basal joint extends downward and curves fornrard. and 

 inward to form the cutting-edge. The molar tubercle arises from the concave inner 

 surface of the basal joint and extends inwards to meet its fellow on the other side, at a 

 point above and somewhat posterior to the cutting-edge ; it is large and strong, but not 

 so stout as in Phreatoicus australis. A view of the outer convex surface of the mandible 

 with the palp attached is shown in fig. 5 ; in this the molar tubercle is of course com- 

 pletely hidden from view ; it will be seen that there are a few setae at the base of the palp 

 on the side toward the base of the mandible, a small row of fine hairs on the other 

 side of the palj), and another on the inferior edge of the basal portion of the mandible. 

 The figure that I origiiially gave of the mandible of Phreatoicus typicus [23, pi. iv. fig. 5] 

 is almost the reverse of the one now referred to, and shows it from the inner side as it 

 rests on its rounded outer surface — its most natural position when dissected out ; the molar 

 tubercle then projects directly upward and only its extremity is shown. 



As usual, the two mandibles difi'er slightly in the cutting-edge. In the right mandible 

 there is only the one cutting-edge formed by the extremity of the basal joint itseK ; this 

 appears usually to consist of three teeth only. In the left mandible (fig. 6) the 

 corresponding part is formed of four teeth, two long ones of equal length and the other 

 two shorter; in addition to this there is the secondary cutting-edge, comj)Osed of three 

 teeth on a process which arises inside and extends parallel to the outer cutting-edge 

 almost as far as its extremity. At the base of this and between it and the molar tubercle 

 is another projection nearly as broad as long, having its extremity rounded and bordered 

 by a double I'ow of stout setae ; the outermost of these are short, stout, and denticulated ; 

 the inner ones, nearer the molar tubercle, become gradually longer, more slender, and 

 plumose instead of denticulate. This process is the same in both mandibles. 



The mandibular palp (see fig. 5) is the same in both mandibles ; the first joint is 

 short, only half as long as the second, and bears several long setae at its extremity ; the 

 second joint is oblong and bears three tufts of setae ou its lower margin toward the eud 

 and another tuft at the extremity ; the third joint is fully as long as the second, and is 

 usually bent upward and inward at right angles to it. Its anterior margin is slightly 

 concave toward the distal end, and bears two regular rows of slightly curved, coarsely 

 plumose setae ; those at the basal end of the row are very short, but the others gradually 

 lengthen distally till the terminal one is about as long as the portion of the joint bearing 

 the row. 



The lower Up (fig. 7) consists of two lobes narrowed at the base, ovate in shape, with 

 the extremity rounded ; the inner margins are fringed mth long setae projecting radially 

 inward, those toward the extremity being the longest. On the outer margins about 

 the middle is a thick tuft of finer setae, and nearer the base another group of shorter 

 setae forming a sort of fur, Avhich extends ou to the surface of the lip. The two lobes are 

 quite divided aluiost to the base, where they appear to be connected with a soft membrane ; 



25* 



