The appendages of the sixtli somite are the 2iid maxillse. All their parts 

 are thin and foliaceous. The coxopodite and basipodite resemble those of the 

 1st maxillge, except that each is deeply cleft into two lobes. There is a tapering 

 endopodite, and a leaf-like exopodite, which last, being used to bale out the 

 branchial chamber in the course of respiration, goes by the special name of 

 scaphognathitn. 



4. Of the Segments and Appendages of the Thora,r. 



The individuality of all eight thoracic somites is maintained by the sterna, 

 which can be seen without removal of the carapace, and by the epimera which 

 can only be seen after the carapace is removed. The individuality of their 

 pleura and terga is entirely lost, but it is possible that the slightly-raised lateral 

 and posterior borders of the carapace represent these elements. We need, 

 therefore, consider in detail only the appendages. 



The fate of the terga and pleura of the thoracic somites has ahead}' been incidentally con- 

 sidered in dealing with the composition of the carapace. 



I have adopted with slight modification the views of Milne Edwards I., that the carapace is 

 formed by the terga and pleura of the aptenno-mandibular somites, and that these elements of the 

 thoracic somites are practically unrepresented in the carapace. 



It must be admitted however that the sculpturing and sutures of the carapace admit of other 

 equally reasonable interpretations. For instance, Huxley {The Crayjlah, p. 166) taught that that 

 part of the carapace which lies in front of the cervical groove represents the terga and pleura of 

 the head ; while of that part which lies behind the cervical groove, the median region represents 

 the terga, and the lateral regions represent the pleura, of the thoracic somites. The sutures 

 of the carapace of Thalassina certainly support this interpretation, and even in the carapace of 

 Nephrops there are grooves and spines which hiirmonize with it. 



The first pair of thoracic appendages are the 1st maxillipeds. They consist 

 of a protopodite, endopodite and exopodite, with, in addition, a leaf -like appendix 

 having the same function as the scaphognathite and known as an epipodite. The 

 protopodite is formed of a leaf-like coxopodite and basipodite similar to, only 

 larger than, the same elements of the 1st maxillte : the endopodite is a thin two- 

 jointed leaf ; the exopodite, which is longer and slenderer than the endopodite, 

 ends in a truncated y?a(7e//«<Jrt ; the epipodite is attached to the outer end of the 

 coxopodite. Their function, like that of the next two pairs of appendages, is 

 partly manducatory, partly respiratory, and in structure they are intermediate 

 between maxillae and ordinary maxillipeds. 



The second pair of thoracic appendages are the 2nd maxillipeds. They 

 are foot-jaws in which their function as organs of mastication has not disguised 

 their resemblance to the ordinary appendages of the thorax. They consist of a 

 protopodite, an endopodite, an exopodite, and an epipodite to the base of which 

 a rudimentary gill-plume or podobmnch is attached. The protopodite consists 

 of a short coxopodite and basipodite : the endopodite, which is larger and longer 



