374 MR. \V. F. LANCHESTER ON THE [Dec. 2, 



than the capitulum, white and semi-transparent ; in both, how- 

 ever, it is thickly studded with minute chitinous papillae (as in 

 D. warwickii). 



The 1st cii-rus is only | of the length of the 6th, is distant by 

 the thickness of its own pedicel from the 2nd, and has its rami 

 equal ; the rami also of the other cirri are equal. The caudal 

 appendage is exactly as long as the pedicel of the 6th cirrus, but 

 appears longer to the naked eye owing to the presence, at its tip, 

 of numerous hairs as long as the joint itself. 



As regards the mouth-parts, the outer maxillae are ovoid, with 

 their inner sides folded over outwardly and their outer surfaces 

 covered with longish hairs ; the inner maxillfe each present an 

 incision on their border by which are formed two low step-like 

 projections, the inner being the smaller, and each bears 1 3 spines, 

 of which the one at the inner angle is much stouter than the 

 rest. The mandibles have 5 teeth, the strongest of which forms 

 the inner angle. The palpi are bluntly conical, with hairs along 

 their outer edges. 



The penis is rather thick, and only begins to taper just before 

 its distal end ; along its length are several exceedingly short hairs. 



This species seems to me to bridge over the narrow gap between 

 the genera Dichelaspis and Foecilasma, in relation on the one side 

 with the Dichelaspids generally, and on the other side with 

 Pcecilasma tridens Auriv. in particular. My gi-ounds for placing 

 it in the former of the two genera are (a) the connection between 

 the two portions of the scutum, and {h) the extension of the 

 carina between the terga ; these two points clearly bring it 

 within Darwin's definition of his genus. At the same time, the 

 bridge of tissue connecting the two parts of the scutum is 

 extremely narrow, so that I was, for some time, for considering 

 the two portions as separate valves and for referring the species 

 to the genus Pcecilasma ; while, on the other hand, the carina 

 in Pcecilasma tridens also extends between the terga, though 

 only by -J- of its length. This species, moreover, has a point in 

 common with those of Pcecilasma, and differing from those of 

 Dichelaspis, namely, the close apposition of the valves. 



But its relationship with both these genera is clearly shown, on 

 the one hand, by the yet present connection between the two 

 parts of the scutum and the extension of the carina between the 

 terga ; and, on the other hand, by the almost complete severance of 

 the scutal segments and the close apposition of the valves. And 

 thovigh its possibly closer relationship to one of these genera 

 relieves me of the responsibility of uniting two genera which 

 Darwin separated after the study of a greater number of species, 

 still I feel that there can be little doubt but that the tie between 

 these genera is exceedingly close. 



There are also some specimens taken from the extreme base of 

 the chelipedes and from the long epipodite of the 3rd maxillipeds 

 of Neptunus gladiator. On the same crab were the specimens of 

 the species next described. 



