THE MYSIDACEA 



173 



a: 



beyond the eye ; in Boreomysis scyphops the distal end of the peduncle 

 is expanded and excavated in a cup -like form and is without 

 pigment or any trace of ocular structure, but in other species of 

 the same genus the eyes are normally developed ; in some Petal- 

 ophthalmidae the peduncles are leaf-like or spiniform ; while in 

 Psewlomnia, AmUyops, and some allied genera, they are repre- 

 sented by broad plates extended 

 horizontally in front of the carapace. 



In the Mysidae the three-seg- 

 mented peduncle of the antennules 

 carries in the male sex, in addition 

 to the two flagella, a conical process 

 beset with numerous sensory fila- 

 ments. 



The antennae have the protopodite 

 distinctly composed of three segments 

 (Fig. 101, 1, 2, 3). A lamellar ex- 

 opodite or " scale " (sc) is always 

 present except in Arachnomysis and 

 allied genera, where it is represented 

 by a spine. In many Mysidae it is 

 divided into two segments by a trans- 

 verse suture near the tip. 



The mandibles have generally a 

 well -developed lacinia mobilis (Fig. 

 102, l.m), differing in form on the 

 two sides, and a row of spines (s) in- 

 terposed between the incisor and 

 molar processes. The row of spines 

 is absent in the Lophogastridae and 



th 1 . 



-- o. 



FIG. 101. 



Cephalothoracic region ofAfysis relicta, 

 young female, from below. Most of the 

 thoracic appendages have been removed, 

 a', external flagellum of antennule ; a", 

 . , . ttagellum of antenna ; ex, exopodites of 



and SOme Mysidae, and thoracic appendages ;l, labrtim ; mil, palp 

 of mandible ; o, oostfgites, not yet fully 

 developed ; sc, scale or exopodite of an- 



,i i VM- 



in SOme Cases the laClllia mOblilS IS 



wontinfr TliA mnlnr -nrnpooa is email tftnll a ! th l -th 3, first, second, and third 



wanting. nan thoracic ai ,p enda ,, PS : ^ L)J 3 ; tlie three 



segments of the protx>podite of the an- 

 tenna. (After Sars.) 



^ 



Or absent in a few Mysidae. A palp 

 . , ,* *\, r 



is always present, and becomes greatly 



enlarged in the aberrant Petalophthalmus, where it appears to have 



a prehensile function. 



The maxillulae (Fig. 103, A) have two endites arising, according 

 to Hansen, from the first and third segments, and a slightly 

 developed laminar exite, which Hansen states belongs to the first 

 segment. In the genus Gnathophausia (Fig. 104) a palp of two 

 segments is present, directed backwards beneath the carapace like 

 that of the Leptostraca. 



The maxillae (Fig. 103, B) have a complex structure. There 

 are two endites corresponding to the second and third segments 

 (Hansen), the first of which is incompletely and the second com- 



