454 Mr. C. Spence Bate on the British Diastylidse. 



form between the higher and the lower types (PI. XIII. figs. 7, 8). 

 The maxilliped (fig. 10) partakes more essentially of the higher 

 type than that of the lower forms ; it is pediform, and consists of 

 a stout basal joint supporting five terminal smaller ones, the last 

 of which ends in an extremely fine point ; three large plumose 

 Lairs are given ofi^ from the penultimate and antepenultimate 

 articulations. To this pair of limbs are attached the branchial 

 appendages, which consist on each side of eight or nine secondary 

 saccular caeca, connected with a common membranous chamber 

 iu which the blood circulates for its perfect aeration. 



The two gnathopoda (or second and third maxillipeds) are 

 developed upon the true type of the Macroura ; the anterior 

 (fig. 11) does not possess the secondary palpi, whereas the pos- 

 terior (fig. 12) does, and moreover is developed so as to become 

 the closing operculum to the mouth. The basal joint is long 

 and broad, and its internal margin is fringed with a row of hairs, 

 which answers to a corresponding row of teeth-like prominences 

 in the true Macroura, where they perform the part of an efficient 

 biting apparatus ; the upper extremity of the joint extends on 

 the outer side, slantingly forwards, and is crowned with hairs. 

 The five terminal articulations are short and unimportant, the 

 whole not equalling the first joint in length. This pair of limbs, 

 together with the preceding, is attached each to one of the first 

 two rings of the thorax, the sternal portion and lateral walls of 

 which are alone developed. 



The next succeeding pair of feet are those which homologize 

 with the great cheliform limbs of the Decapoda (fig. 13) ; they 

 are the most powerfully formed organs which the animal pos- 

 sesses, are considerably longer than any of the others, and reach 

 anteriorly beyond the extreme limits of the antennse. Each is 

 formed of an anteriorly curved basal joint, three succeeding 

 posteriorly curved articulations, the three together equalling in 

 length the preceding, and two others which appear to be more 

 freely jointed than any of the preceding, and which together 

 equal in length the basal articulation. The basal segment is 

 ciliated upon the convex or posterior margin, the three suc- 

 ceeding are furnished with long plumose cilia upon the anterior 

 margin, and the terminal one has long simple hairs upon the 

 posterior margin only. Arising from the coxa, which in the whole 

 family is closely associated and probably anchylosed with the 

 segment of the body, is the palpe (of M.-Edwards's earlier 

 writings, the exognathe of his later), — a secondary appendage to 

 the legs peculiar to the Stomapoda ; it consists of a single arti- 

 culation, and a terminal ciliated stalk or filament {tige) equalling 

 in length about half that of the true leg. 



