48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



1^2. Musculus abductor Hagelli II pedis spurii (fig. 14 B). — Like 

 the corresponding muscle in the first abdominal appendage, this muscle 

 arises on the lateral part of the wall of the basipodite and terminates 

 on the proximal preaxial border of the flagellum, which is brought 

 away from the center as well as slightly forward by its action. 



THE FEMALE 



The first and sixth abdominal segments of the female blue crab 

 lack appendages. The second, third, fourth, and fifth segments each 

 have pleopods which become increasingly smaller posteriorly. The 

 coxopodite and basipodite are separated by a membrane on the post- 

 axial surface ; preaxially the two are fused. A description of the 

 muscles pertaining to the first abdominal appendage, attached to the 

 second abdominal segment, applies to the other three pairs of abdomi- 

 nal appendages, in which the muscles are similar but weaker. 



z/j. Musculus promotor coxopoditis I pedis spurii (fig. 14 C). — 

 This muscle arises on the dorsal border of the second abdominal seg- 

 ment and is inserted on the middle of the preaxial proximal border 

 of the coxopodite, which it brings strongly forward. 



124. Muscidus abductor coxopoditis I pedis spurii (fig. 14 C). — 

 This muscle likewise originates on the dorsal border of the second 

 abdominal segment lateral to the origin of the promotor. It passes 

 slightly outward to its insertion on the extreme lateral proximal border 

 of the coxopodite. The appendage is moved away from the midline 

 by its action. In the three pleopods which follow this one, the abductor 

 of the coxopodite takes its origin below and behind that of the pro- 

 motor muscle, so that in the last pleopod it is nearly obscured by the 

 promotor when viewed preaxially. This is the only noteworthy differ- 

 ence in any of the muscles of the following three appendages as com- 

 pared with those of the first appendage, except that they become 

 smaller as the appendages themselves decrease in size. 



775. Muscidus adductor coxopoditis I pedis spurii (fig. 14 C). — 

 This muscle is much larger than its opponent, the abductor. It arises 

 on the median dorsal border of the second abdominal somite from 

 almost the midline to the origin of the promotor. It is inserted at the 

 extreme median proximal margin of the coxopodite, which it pulls 

 inward and forward. 



lyd. Muscidus reductor basipoditis I pedis spurii (fig. 14 C) . — This 

 is a very short but rather powerful muscle arising laterally along 

 the proximal posterior border of the coxopodite at the only place 

 where the fusion is not complete between basipodite and coxopodite. 



