70 



The accessory muscles are situated entirely within 

 the scaphognathite itself. Their function is to bend the 

 scaphognathite during the process of lifting up or extend- 

 ing the latter. 



There are two muscles which arise close together on 

 the inner side of the insertion of the inner flexor of 

 the scaphognathite. They extend outwards into the 

 middle and inner portions of the scaphognathite. 



The anterior accessory (a. ace.) divides into two parts, 

 each of which is attached to the anterior wall of the 

 scaphognathite. 



The posterior accessory (p. ace.) also divides into two 

 parts. One division appears to be inserted on the 

 posterior wall and the other on the anterior wall. 



VII. First maxillipede (fig. 29). Only the 

 extensor and flexor of the Coxopodite need be noted here. 



The extensor (e. C.) arises on the epimeron of this 

 somite. It passes downwards and inwards between the 

 two flexors of the flabellum and behind the extensor of 

 the latter (see below). It is inserted near the outer and 

 posterior margin of the coxopodite. 



The flexor (/. C.) arises at the upper side of the 

 posterior face of the last cephalic endopleurite on the 

 inner side of the point where the latter fuses with the 

 second thoracic endosternite. It passes directly down- 

 wards as a narrow muscle, and is inserted on the 

 anterior margin of the coxopodite. 



The muscles of the exupudite have the same arrange- 

 ment as the similar parts in the third maxillipede. 



The muscles of the flabellum are large and powerful. 

 The fiabellurn lies on the dorsal side of the gills, and by 

 repeated rhythmical movements keeps the surface of the 

 gills free from sand and mud. 



