ISOPODA. 29 



appendages are lost ; they are, however, uninjured in the smaller speeimcn. The lirst 

 appendage of this scries, the seeoud of the niesosonu', comprises .six joints, tlie first of which 

 is large and stout, the rest progressively decrease in size,* and all are lilierally provided 

 with small arborescent chromatophores. The second joint Jias two serrations on its 

 outer or ventral side, at each of whicli are a few long setaa, distally, both ventrally and 

 dorsally, but not laterally ; there is also a distal fringe of long setae ; the following joint 

 has a single serration, the next has three, and the setae connected therewith are 

 distinctly spinous ; the penultimate one has seven of these so-called serrations, l>ut very 

 small at first, increasing in size distally ; the setae they bear are very small at first 

 but increase to long ones distally, on the opposite side of the joint the distal fringe is 

 long and spinous. The ventral margin is slightly expaiideil and flattened as a blade, 

 chieHy proximally. The sixth joint or dactylus is stout and capable of foMing'on the 

 preceding one in a subehelate manner. This appendage constitutes a secondary 

 sexual character in the adult animal wliere it becomes modified to form a prehensile 

 organ, and differs considera])ly from the remainder which are distinctly locomotive in 

 function. As such it is figured and very briefly described by Eights. For this species 

 or S. c&rnuta, neither Dr. Studer nor I\lr. Beddard give any description of this 

 appemlage as distinct from the otliers, though both refer to its modification generally 

 among members of the genus. From this and other circumstances as previously indicated 

 it may be assumed that their specimens were immature. The other thoracic appendages 

 are alike in structure, the propodal joint is slender and not in any way expanded, 

 nor does the dactylus appear capable of being reflexed upon it in a subehelate 

 manner. The spinous armature varies with the size of the liml) or the joint where 

 it occurs, and the last appendage of the mesosome only differs from the others in size. 



Uf the abdominal appendages the first three pairs are adapted for swimming. 

 The ])ase of each liml> is roughly in the form of a truncated cone directed towards the 

 middle line, and articulated to the sternum near one corner of the narrow base which 

 is curved outwards ; this angle bears three stout setae on the first and two on the 

 remaining appendages, other fine setae fringe these joints tliroughout. 



The exopodite is a delicate .semicircular structure fringed with fine seta), and on 

 its curved Itorder with long plumose setae. The endopodite is smaller and attached to 

 the protopodite at altout two-thirds of its length ; this shows more distin(;tly a ribbed 

 structure, each rib corresponding to a long plumose setae. The three pair of appendages 

 do not differ materially in shape or structure except that the straight posterior border 

 is prolonged into the "penial filament." This is a slender rod-like body passing 

 towards the middle line, it then bends somewhat al)ruptly backwards, and is grooved 

 on its inner side. It is about 45 mm. long, and appears to be jointed at the bend; 

 but this is probably due to injury, as there is no trace of such a structure in the 

 smaller specimen where, moreover, this organ is very much smaller. This organ of 

 the larger .specimen is very much .smaller than that indicated in Eights' figure. 

 In their description of S. cornuta neither Dr. Studer nor Mr. licildard allude to it. 



