370 JOURNA L, BOMB A Y NATURAL HISTORY SOCIETY, Vol. XVIII. 



attached, the latter of a variable number of segments, the endopodite 

 of five, isohiopodite, meropodite, carpopodite, propodite and dactylo- 

 podite, enumerating from base to tip. 



All the appendages may be regarded as built on the same plan, 

 and all their variations in appearance and function are due to one or 

 more of three factors — 



1. Suppression or atrophy of a part or parts. 



2. Union or coalescence of parts. 



3. Modification of a part or parts. 



The third maxilliped much resembles the second, but is consider- 

 ably larger and stouter. The expodite is however completely sup- 

 pressed, though in the Lobster and Prawn it is well developed. 



The epipodite has both gill and leaf. The basipodite is firmly 

 ankylosed with the ischiopodite as in all the thoracic limbs of Pali- 

 nurus, the line of union being better marked than in the second 

 maxilliped by a constriction forming a complete ring. The meropo- 

 dite is in this limb the longest segment. All pieces of the endopodite 

 are somewhat triangular in transverse section, being less flattened 

 than the second maxilliped. The apex of the triangle forms the outer 

 margin of the endopodite, the base being flat and well covered with 

 bristles. Tne dactylopodite is much longer than that of the second 

 foot-jaw and is covered with hairs. 



The maxillipeds and maxillae are all directed forward in the hori- 

 zontal plane, so as to overlap one another, below the opening of the 

 mouth. 



The first maxilliped is much modified. The two segments of the 

 protopodite have become b/oad thin plates with an inner thin cut- 

 ting edge fringed with stiff setae. The epipodite has become a thin 

 membranous plate with no trace of a gill. 



The endopodite is a small oval plate, its inner margin setose. The 

 exopodite is relatively very large. Its proximal joint forms more 

 than half its length ; the remaining nine joints are much broader 

 than long and together form an oval plate fringed with setae, and 

 twisted at the base through an angle of about 150 degrees, so that the 

 anatomical inner surface looks outward. 



The walking limbs are much alike. The first is the shortest and 

 stoutest. Tne coxopodite, short and irregular in shape, bears at its 

 outer dorsal angle an epipodite, the proximal portion of which is calci- 



