174 



THE CRUSTACEA 



A. 



Fio. 102. 



pletely divided into two. A plate -like lobe on the outer side (/) 

 is regarded as the exopodite and springs from the third segment 

 (Hansen). The palp is composed of two segments. In Gnatho- 

 phausia a pigmented papilla on the outer side close to the base 

 bears the opening of a gland producing a luminous secretion. 



The thoracic appendages have 

 the coxopodite very small, and 

 have usually an exopodite con- 

 sisting of a peduncle and a 

 lm--_Y:ju,~ \ multi-articulate setose flagellum 

 attached near the proximal end 

 of the basipodite. The ex- 

 opodites of the first pair may 

 be reduced (Lophogastridae, 

 Eucopiidae) or absent (some 

 species of Gnathophausia, Petal- 

 ophthalmidae), and those of the 



A, mandible of Mysis. B, oral edge of same, j , r> i 



further enlarged, i, incisor process ; l.m, lacinia SCCOnd. pair are absent in retal- 

 mobilis;m, molar process ; S ,8 P ine-row. (Aafter ophthalmus. 



The first pair of thoracic 



limbs are always specialised as maxillipeds. In the Lophogastridae 

 and Eucopiidae they are without distinct endites. In the Mysidae 

 (Fig. 105, A) an endite is generally borne by the basipodite, and 

 sometimes also by each of the two following segments. In Petal- 

 ophthalmus the first and second thoracic limbs (in the other genera 

 of Petalophthalmidae only the . \* 



second) have a large lamellar 

 endite developed from the 

 meropodite. 



In the Lophogastridae 

 (Fig. 106) the last seven pairs 

 of thoracic limbs are all 

 similar, and exhibit the usual 

 number of seven segments, 

 the dactylus being large and 

 having generally a claw-like 

 spine at the apex. In the 



TTiirnniirlap thp sprrnirl tn thp resulting from the division of a single endite 



^UCOpliaae tne I tO me responding to the third segment, and the segn__ 



fifth pairs are Subchelate. and here numbered 5 and 6 become 4 and 5 respectively) ; 



*_.,*" i . i i /, flabellum or exopodite. (After Hansen.) 



the next three pairs, which 



are exceedingly long and slender, have also the dactylopodite flexed 

 against the propodite to form a prehensile organ. In the Mysidae 

 there is, as a rule, a distinction between the second and the follow- 

 ing limbs. The former, sometimes called second maxillipeds or 

 "gnathopoda," are bent inwards towards the mouth, with the 

 normal number of segments and with a rounded dactylopodite 



-a. 



"2. 



T---6. 



--S. 



f. 



FIG. 103. 



A, maxillula, B, maxilla, [of Mysis oculata. 1-6, 

 segments of the appendages ; I i-l 4 , endites of the 

 respective segments according to Hansen's earlier 

 interpretation (in his later papers the endftes here 

 numbered 3 and 4 in the maxilla are regarded as 



cor- 

 segments 



