THE MYSIDACEA 



173 



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 

 Pseudomma, Amblyops, 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, Lm), differing in for-m 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 .--- 



-ex. 



-' O. 



FIG. 101. 

 Cephalothoracic r 



rdicta, 



. 



EuCODiidae and SOme Mysidae, and thoracic appendages ; j, labrum ; tad, palp 



,1 i v ! of mandible; o, oostegites, not yet fully 



in SOme Cases the lacinia moblllS IS developed ; sc, scale or exopodite of an- 



wonfiTio- Thp mnlar nrrr>p<n' <small tenna ; th i-f h 3, lirat, second, and third 



Wanting. ine molar process IS Small thoracic appendages; I, 2, 3, the three 



Or absent in a few Mysidae. A palp segments of the protopodite of the an- 

 -\ r , r tenna. (After Sars.) 



is always present, and becomes greatly 



enlarged in the aberrant PetalophMwlmus, 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- 



