CRUSTACEA. 147 



It is impossible to give any general view of the appendages 

 of a Crustacean ; but it may be as well to name the appendages 

 which are present in one of the higher forms, 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 "cephalo- 

 thorax," which is protected above by the " carapace," 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 exopodite, which are nearly 

 of equal length. The third segment of the head carries a pair 

 of very long feelers, which are known as the " great antennas." 

 Each consists of a short propodite and a long and jointed 

 endopodite, with a rudimentary exopodite. Thefourt/i seg- 

 ment of the head carries a pair of jaws, which are known as the 

 ".mandibles." Each mandible 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 man- 

 dibles also is placed the aperture of the mouth, which is 

 bounded in front \yy a plate, known as the "labrum" (upper 

 lip) or " hypostoma." and behind by a forked plate, known as 

 the " labium " (lower lip) or " metastoma." Thefift/i 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 " maxilli- 

 pedes." Each foot-jaw is merely an ordinary limb, consisting 

 of propodite, 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. The eleventh 

 segment (the fourth of the thorax) carries a second pair of 

 limbs, also " chelate," but much smaller than the preceding ; 

 and the twelfth segment (the fifth of the thorax) carries another 

 pair of the same. The thirteenth segment (the sixth of the 



