MUSCULAR AND ALLIED SYSTEMS. 95 



muscles belonging to this region are rudimentary. The 

 muscle-fibres are transversely striated. 0. 0. 61 B. 

 Parker & Rich, Macleay Memorial Volume, p. 159. 



C. 25. Muscles of some right appendages of a Lobster (Homarus 

 vulgar is). 



A. Proximal part of a thoracic appendage showing the 

 muscles of the two basal podomeres coxopodite and basi- 

 podite. Owing to the shortness of these two segments, 

 their muscles move the limb as a whole, giving rise to 

 adduction, abduction, elevation, and depression. The 

 muscles of both podomeres rise from the endophragm. 

 They are indicated by numbers, thus : 1. Flexor of 

 coxopodite = adductor of limb. 2. Flexor of basipodite = 

 levator of limb. 3. Extensor of basipodite-= depressor of 

 limb. 4. Extensor of coxopodite = abductor of limb. 



B. An abdominal appendage. The muscles are simple 

 in their arrangement and produce backward and forward 

 movements of the limb and abduction and adduction of the 

 exopodite. 1. Extensor. 2. Flexor. 3. A complex mass 

 of muscle, the proximal part of which forms a continuation 

 of 1 & 2, while the distal part is composed of adductor 

 and abductor of the exopodite. 



C. The Mandible. The adductors (1, 2, 3) are both 

 numerous and powerful, the abductors (4, 5) compara- 

 tively weak. 



D. The Tail-fin and Telson. The main muscles are 

 those concerned with flexion (1) and extension (2) of the 

 tail-fin. Besides these, there are muscles (3, 4) for the 

 adduction of the fin as a whole and (6, 8) of the exo- 

 podite, as well as (5, 7) for the abduction of the exopodite. 

 The last four muscles would also to a certain extent have 

 powers of extension and flexion. 0. C. 61 C. 



C. 26. A section of the claw of a Lobster (Homarus vulgaris), 

 showing the fibres of the penniform muscle arising from the 

 propodite and inserted into the apodeme of the dactylopo- 

 dite. 0. C. 60. Hunterian. 



