Crangon and Galathea. 85 



ischium are connate, their line of junction marked by a suture, their inner edge 

 dilated, and generally finely serrated ; they are also often hirsute and toothed. 

 The meros, carpus, and propodos, are slender, generally denticulated and hairy. 

 The dactylos is blunt at its extremity, and hairy. The comparative lengths of 

 the ischium and meros afford valuable specific distinctions. 



The abdomen generally equals the carapace in length, and is as broad as 

 the posterior margin of that organ ; it is flattened from above downwards, and 

 each of its somites sculptured transversely ; the sixteenth to twentieth somites 

 bearing well-developed coxa ; in the fifteenth the coxa is absent in the 

 females. 



The telson (twenty-first) is triangular, submembranaceous, with a varying 

 number of chitinous plates, thickened with carbonate of lime scattered through- 

 out; it is also vmappendiculate. 



The abdominal appendages vary in the sexes. 



I. In the males (Plate X., 15, 16, 17-20, left-hand side of plate). 



First abdominal pair (fifteenth pair; anterior pleopod Spence Bate) coxa 

 sparingly developed and connate with somite, which is expanded outside it ; 

 basis and ischium flattened, the latter membranaceous ; somite developed infe- 

 riorly. 



Second abdominal pair (sixteenth pair). Coxa3 soldered to somite, well 

 developed, basis small ; ischium and meros flattened, the latter membranaceous. 



Third to fifth (seventeenth to nineteenth). Coxa well developed, connate; 

 basis dilated into a truncated scale ; ischium and meros very short, cylindrical, 

 arising from a notch in side of basis, and barely attaining its apex. 



II. In the females (Plate X., figs. 16, 17—19, right-hand side of plate). 

 First abdominal somite unappendiculate. 



Second abdominal somite (sixteenth). Coxeb soldered; basis, ischium, and 

 meros elongated, flattened, ciliated along edges ; the apex of meros rounded. 



Third to fifth (17th to 19th) as last, except that the meros (incorrectly 

 marked c in plate) is acuminate. 



Sixth abdominal somite (twentieth pair). Coxa3 connate ; basis flattened, 

 broad, articulated to coxa, and by a small lateral process to telson ; furnished 

 on its inner side with a flattened squamiform appendage (but vide infra, Gal. 

 squamifera, p. 92). 



VOL. XXIV. N 



