24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



corner of the endosternite, running inward and forward to its insertion 

 on the inner proximal border of the coxopodite. It pulls the coxopodite 

 strongly backward and thus toward the center. 



61. Musculus adductor endopoditis II maxillae (fig. 8) . — This slen- 

 der threadlike muscle arises on the inner proximal part of the coxopo- 

 dite, passing laterally to its insertion on the cuplike swelling at the 

 lateral outer border of the endopodite. It causes the endopodite to be 

 bent somewhat toward the inner region. 



62. Musculus flexor scaphognathitis II nmxillae (fig. 8). — This 

 muscle originates in the cuplike thickening that borders the outer part 

 of coxopodite and endopodite, and runs outward with pronounced 

 ramification through the scaphognathite to its attachment on the car- 

 tilaginous fold which parallels the outer border of the scaphognathite. 

 This segment is bent by means of the flexor muscle. In Pandalus there 

 is an additional superior flexor muscle which is unbranched. 



6^-69. Musculi respiratorii II maxillae (fig. 8). — Arising on the 

 dorsal surface of the endopleurite just mesal to the origin of the 

 promotor, the first of these muscles, musculus respiratorius primus 

 (63), goes forward and outward beneath the promotor to its insertion 

 on the lateral part of the skeletal swelling between coxopodite and 

 scaphognathite. This and the remaining respiratory muscles induce a 

 strong undulating motion in the scaphognathite, thus forcing the water 

 that is drawn into the gill chamber to flow forward. The second 

 muscle, musculus respiratorius secundus {64) , heavy and powerful like 

 the first, arises mediodorsally on the head apodeme, runs outward and 

 forward, and passes above the first and below the promotor to reach 

 its insertion just over the first. The third, musculus respiratorius 

 tcrtius ((55), is a small and slender muscle completely hidden until the 

 more dorsal muscles are removed. It originates on the thickened 

 skeletal ridge on the anterior part of the head apodeme, and runs for- 

 ward and slightly outward to its insertion on the skeletal swelling of 

 the scaphognathite just below the insertion of the remoter. The 

 fourth, musculus respiratorius quartus (66), is an exceedingly heavy 

 but short muscle arising under the third on the same skeletal ridge of 

 the head apodeme, running outward to its insertion on the scaphog- 

 nathite, between two angles of the skeletal swelling marking its proxi- 

 mal border. The fifth, musctdus respiratorius quintus ((5/), is a small, 

 powerful muscle arising on an infolding of the apodemal membrane 

 behind the fourth, then passing forward and slightly inward to its inser- 

 tion on the skeletal swelling just beneath the insertion of the promotor. 

 The sixth muscle, musculus respiratorius sextus (68), arises on the 

 same infolding just lateral to the fifth, and proceeds straight forward 



