1272 THE VOYAGE OF H.M.S. CHALLENGES. 



sword-shaped, triangular as far as the half of their length, with the lower angle denticulate 

 at the base, three and a half lines long, flesh-coloured with two lines of orange-red dots ; 

 they are supported on a short cylindrical peduncle. Lower antennse filiform, white, 

 much longer than the upper, formed of six joints, the first of which is much longer than 

 the rest. Eyes very small, round, orange-red, placed on the outer side at the base of the 

 upper antennse. Thorax of seven segments, which increase gradually in width to the 

 fifth; the sixth and seventh are narrower. Abdomen of four rings, narrower, but longer 

 than those of the thorax, so that the whole of the animal appears as if divided into two 

 portions, the anterior half wider, the hinder abruptly narrowed. Seven pairs of legs 

 properly so called, simple, slender, which in their length preserve the order of the segments 

 of the thorax; 1 the fifth pair, the longest of all, is denticulate on the outer side through 

 the whole length of the second joint, which on the inner side is prolonged beyond the 

 articulation in an acute point. The tail carries six very slender stiles ; four inserted on 

 the same line, and the other two lateral, somewhat lower and longer than these." 



It is possible that the notes of colouring' 2 given by Prestandrea may suffice to 

 determine whether his species be the same as Tyro marginata, Bovallius, which is also 

 from the Mediterranean, but in the latter species the eyes are said to be very large. 

 Tyro comigera, Milne-Edwards, agrees with Prestandrea's species in having " face 

 superieure de la tete garnie de deux petites cretes obtuses et divergentes." 



For the original definition of the genus Tyro, see Note on Milne-Edwards, 1840 

 (p. 189). It will be noticed that Milne-Edwards says that "the lower antennae are 

 extremely small," while Prestandrea says that they are much longer than the upper, but 

 the apparent discrepancy can be explained by a reference to the description of Clydonia 

 borealis, in which Sars states that "the lower antennas of the female are altogether 

 rudimentary, almost inconspicuous, those of the male elongate, very thin, filiform, 

 geniculate." For the definition of the genus Clydonia, see Note on Dana, 1849 (p. 229). 

 The identity of this genus with Tyro, Milne-Edwards, was pointed out by Bovallius in 

 1885, but Bovallius does not describe the lower antennae in any of the nine species 

 which he refers to this genus. It is therefore probably from the. male of Clydonia 

 borealis, as described and figured by Sars, that, in the diagnosis of the family Tyronidae, 

 he draws the character of the lower antennae as " angularly bent, fixed at the inferior 

 side of the head." The definition which Bovallius gives of the genus is as follows : — ■ 



" Head truncated anteriorly. First pair of antennae very robust, long, occupying 

 with their basal joints the largest part of the anterior side of the head. First two pairs 

 of pereiopoda [first and second gnathopods] simple, not cheliform. Fifth pair [third 



1 The meaning no doubt is that the shorter legs are attached to the shorter segments and the longer legs to the 

 longer segments, but at any rate in some of the species, if not in all, the fourth segment is longer than the fifth, while 

 the limbs of the fifth are longer than those of the fourth, and in Tyro clausii, Bovallius, the short sixth segment has the 

 limbs longer than those of the longer fifth segment. 



2 The colouring of an unpublished figure by Sir J. D. Hooker agrees well with that of Prestandrea's species. 



