174 



THE CRUSTACEA 



pletely divided into two. A plate -like lobe on the outei' 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 exo^Dodite con- 

 sisting of a i)eduncle and a 

 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 

 second pair are absent in Petal- 

 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 Fetal- 

 oplithahnm 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 

 Eucopiidae the second to the 



Fig. lO'i. 



A, mandible of Mysis. B, oral edge of same, 

 further enlarged, i, incisor process ; Liii, lacinia 

 mobilis ; rn, molar process ; *■, spine-row. (A after 

 Bars.) 



Fig. 103. 



A, maxillula, B, maxilla, of Mysls oculata. 1-6, 

 segments of the appendages; H-J'i, endites of the 

 respective segments according to Hansen's earlier 

 interpretation (in his later papers the endites here 

 numbered 3 and 4 in the maxilla are regarded as 

 resulting from the division of a single endite cor- 

 responding to the third segment, and the segments 

 fifth pairs are Subchelate, and here numbered 5 and e become 4 and 5 respectively); 

 >■ , . 1 • 1 /, nabellum or exopodite. (After Hansen.) 



the next three pairs, Avhich 



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 



