SEA-FISHERIES LABORATORY, 357 



V. First maxilla (fig. 20). There are two 

 extensors and two flexors. 



Flexors. One outer (o.e.m.) and one inner (i.e.m.) 

 muscle, which run together and arise from the outer 

 portion of the protogastric region of the carapace. They 

 pass directly downwards together, and when near the 

 maxilla the two separate and are inserted on the outer and 

 inner parts of the coxopoclite respectively. 



Extensors. One outer (o.f.m.) and one inner (i.f.m.) 

 The tops of the two pillar-like portions of the first post- 

 oral endopleurites are joined by a strand of tissue. 

 Beneath the arch thus formed the two muscles arise near 

 the middle line. They pass downwards and slightly 

 inwards, diverging somewhat as they approach the 

 appendage. They are inserted on the coxopodite at the 

 same point as the corresponding flexor muscle. 



YI. Second maxilla. There are two extensors 

 and two flexors. 



Extensors. The inner extensor arises from the 

 j)osterior face of the first post-oral endopleurite. It is a 

 short muscle which passes downwards and slightly 

 outwards, and is inserted on the outer side of the coxo- 

 podite. 



The outer extensor is a long narrow muscle. It 

 arises from the epimeron of this somite just in front of the 

 last cephalic endopleurite. It passes inwards and down- 

 wards across the anterior face of the flexors of the 

 scaphognathite, and is inserted close to the small inner 

 extensor. 



The two flexors are small, and arise close together 

 near to the origin of the outer extensor. They pass 

 directly downwards, and are inserted near together on the 

 inner side of the coxopodite. 



