THE STOMA TOPODA 323 



the limb shows the outer branch to be the endopodite and the 

 inner the exopodite, the relative positions of the two being reversed 

 in the course of development. 



The pleopods (Fig. 190, B, C) are remarkable in carrying the 

 branchial apparatus. The broad and flattened protopodite has 

 articulated with it at some distance from each other the endopodite 

 and exopodite, each of which is lamellar and membranous and is 

 obscurely divided into two segments. From the inner edge of the 

 endopodite springs a short appendix interna (i), bearing a group 

 of coupling-hooks. The branchiae (br) consist of a main stem 

 springing from the anterior face of the exopodite near its base, 

 extending horizontally inwards, and carrying on its lower edge a 



A. 



A, first thoracic appendage of S>n<illa mantis. B, second pleopod, showing the branchial 

 appendage. C, the same, after removal of the branchial filaments, br, branchial appendage ; 

 en, endopodite ; ti>, epipodite ; ex, exopodite ; i, appendix interna. 



series of tufts of ramified branchial filaments. In the female all 

 the pleopods are similar, but in the male the first pair have the 

 endopodite modified. 



The uropods form, with the telson, a broad tail-fan (Fig. 188). 

 The short protopodite runs out into a flattened plate (p) lying 

 between and below the rami, divided distally into two sharp teeth. 

 The exopodite is distinctly divided into two segments. 



Alimentary System. The stomach is large and thin- walled and 

 is divided into two chambers. Its armature is slightly developed 

 as compared with that of most Decapods. The anterior or cardiac 

 chamber is large and extends in front of the mouth as far as the 

 base of the rostrum. In its posterior wall lie two pairs of rod-like 

 sclerites, the upper pair articulating with an unpaired plate which 

 forms the floor of the smaller pyloric chamber and projects as a 

 median keel into its cavity. The intestine is very narrow, but 

 expands somewhat at about the fifth abdominal somite to form the 



