118 PHYSIOLOGICAL SERIES. 



the fin, and is thus able to produce the rotary movements 

 so important in swimming. The fin as a whole can be 

 protracted and retracted by the latero-scapularis and coraco- 

 basalis. 



C. 125. Eight pectoral fin of a Cod (Gadus morrhua), showing 

 the muscles. Deep and superficial layers can be recognized 

 on both surfaces o the fin, in the form of well-defined 

 muscles which cross one another at an acute angle. A 

 small muscle (dilator) is situated along the anterior border 

 of the fin and inserted on the base of the anterior fin-ray. 



C. 126. Right pectoral fin of Penoplitlalmus koelreuteri. The 

 muscles upon the dorsal (inner) surface of the fin are 

 greatly developed, probably in connection with the land- 

 walking habits of the fish and extend for a considerable 

 distance down the fin-rays. 



Hammerle, Bericht. d. Naturforsch. Gesell. Freiburg, 

 Bd. x. 1897, p. 20. 



C. 127. Fore limbs of a Hell-bender (Cryptobranchus alleglian- 

 iensis), showing in the upper specimen the superficial, and 

 in the lower the deep muscles. As in other Urodeles the 

 limb movements are of a very generalized nature without 

 any great precision. The muscles are accordingly simple 

 in their arrangement and mostly have the form of broad 

 sheets. The coraco-brachial muscles are strongly de- 

 veloped, as in, the Reptiles, but as yet there is no repre- 

 sentative of the . biceps unless perhaps the coraco-radialis 

 proprius may be so regarded. The dorso-humeralis gives 

 origin to a very large and extensive dorso-epitrochlearis 

 (anconeus scapulae medius), and is itself in part continued 

 to the humerus upon the outer surface of the arm a 

 course that suggests the condition of the latero-scapularis 

 in the Dog-fish. The superficial extensor and flexor 

 sheets of the fore-arm are each divided into three seg- 



O 



ments. The median of these is attached to the fingers, 

 and the lateral to the radius and ulna respectively. The 

 deep layer is chiefly confined to the hand and distal part 

 of the fore-arm. The following is a list of the muscles, 



