CRUSTACEA. 331 



such as the Lobster, in which all the somites, except the 

 telson, carry a pair of appendages each. The somites of the 

 head and thorax are amalgamated into a single mass, termed 

 the " cephalothorax," which is protected above by the " cara- 

 pace," and carries the appendages on its lower surface. The 

 first segment of the head carries a pair of eyes, which are 

 " compound," and are borne upon long stalks, formed by the 

 propodite of the appendage. The second segment of the head 

 carries a pair of small jointed feelers, which are known as 

 the " lesser antennae " or " antennules." Each consists of a 

 short propodite, and a much-segmented endopodite and ex- 

 opodite, which are nearly of equal length. The third seg- 

 ment of the head carries a pair of very long feelers, which 

 are known as the " great antennae." Each consists of a short 

 propodite and a long and jointed endopodite, with a rudimen- 

 tary exopodite. The fourth segment of the head carries a pair 

 of jaws, which are known as the " mandibles." Each man- 

 dible consists of a large propodite, with no exopodite, but 

 with a small endopodite, which is known as the " mandibular 

 palp." Between the bases of the mandibles also is placed 

 the aperture of the mouth, which is bounded in front by a 

 plate, known as the " labrum " (upper lip) or " hypostoma," 

 and behind by a forked plate, known as the " labium " (lower 

 lip) or " metastoma." The fifth segment carries another pair 

 of jaws, which are known as the first pair of " maxillae ; " 

 whilst the sixth segment carries another pair of the same, 

 known as the second pair of " maxillae." The seventh and 

 last segment of the head carries the first of three pairs of 

 what are generally known as " foot-jaws " or " maxillipedes." 

 Each foot-jaw is merely an ordinary limb, consisting of pro- 

 podite, exopodite, and endopodite, but modified to assist in 

 mastication. The eighth segment (the first of the thorax) 

 carries a second pair of foot-jaws, and the ninth segment 

 (the second of the thorax) bears a third pair of the same. 

 The tenth segment (the third of the thorax) carries a pair of 

 jointed limbs, consisting of propodite and endopodite alone, 

 without any exopodite. These limbs are greatly developed, 

 and their extremities form a pair of pincers or " chelae," so 

 that they constitute the " nipping- claws " of the Lobster. 



