NO. 9 MUSCULATURE OF THE BLUE CRAB COCHRAN 25 



to its insertion on the swelling, directly below the insertion of the 

 third. The seventh muscle, musculus respiratorius septimus (<5p), like 

 the sixth, is short and slender, arising laterally to it on the infolding 

 and being inserted on the swelling midway between the insertions of 

 the fourth and the sixth. 



THE FIRST MAXILLIPED 



The resemblance of this appendage to the maxillae rather than to 

 the typical thoracic appendage has already been commented upon by 

 several authors. The endopodite is weakly developed and devoid of 

 muscles in the blue crab, but as its basal part is partly fused to the 

 exopodite, it naturally partakes of the motion of the exopodite caused 

 by the adductor muscle of the latter. The exopodite is relatively 

 heavily muscled. The muscle extending through the flagellum origi- 

 nates entirely within the proximal segment of the flagellum, which is 

 considerably enlarged. This origin is similar to that found in Astacus. 

 In Pandalus the origin of this muscle is in the basal lobe of the first seg- 

 ment of the exopodite. The extremely poor development of the abduc- 

 tor of the flagellum in Pandalus appears to throw the whole task of 

 moving the flagellum upon the flagellar muscle itself, which therefore 

 needs the wider attachment space. In Astacus and Callinectes, where 

 the abductor of the flagellum is relatively very large, the flagellar 

 muscle is rather slender and weak. 



Of the extrinsic muscles in the first maxilliped of the blue crab, it 

 is possible to name positively only the promotor and the attractor of 

 the epipodite. The small anomalous muscles which take the place of 

 reductor, levator, and depressor have been referred to by number only, 

 as their true function is as yet obscure. Further dissection of other 

 representative decapods may subsequently reveal some species in which 

 the functions of the corresponding muscles will be more apparent, 

 and it may be possible in this way to assign names by analogy to these 

 which it is now inadvisable to attempt to name arbitrarily. 



As in both maxillae, the basipodite of the first maxilliped is no 

 longer traceable as a distinct segment, being either eliminated com- 

 pletely or indistinguishably fused with the coxopodite. Its normal 

 position if it were present may be ascertained in relation to the origins 

 of endopodite and exopodite. In that case it would have lain between 

 the second endite of the coxopodite and the epipodite. 



70. Musculus promotor medialis I pedis maxillaris (fig. 9). — This 

 strong but slender muscle arises on the inner anterior border of the 

 paraphragm between the first and second thoracic segments near the 



