THE LOWER VEUTEBRATA. 



183 



of the paired and that of the median fins an interesting 

 fact. 



Each girdle 

 is a bent bar 

 of cartilage, 

 divisible into 

 dorso - lateral 

 and ventral 

 regions (cf. fig. 

 36), but there 

 is no fenestra 

 dividing up the 

 latter, 

 higher 



Fig. 95. PECTORAL GIRDLE AND RIGHT PECTORAL FIN 

 OF DOGFISH. 



(After Marshall and Hurst.) 



as n 

 types. 



The pelvic 

 girdle has no 

 con nexio n 

 with the ver- 

 tebral column. 



The paired fins are supported proximally by a series of 

 cartilaginous rays, and distally by a series of horny rays 

 much as are the median fins. 



The cartilaginous rays vaguely 

 suggest a multitude of fingers, but 

 we cannot get nearer in our re- 

 semblance to the familiar limbs 

 Instead of a humerus, we find in 

 the pectoral fin three cartilages 

 articulating directly with the girdle. 

 These are called pro-, meso-, meta- 

 pterygium. the order being from 

 pre- to post- axial, and also from 

 smallest to largest. In the pelvic 

 fin, the first two are not recog- 

 nizable, but the corresponding fin- 

 rays articulate directly with the 

 girdle : the meta- is here called 

 basi-pterygium. In the male, but not in the female, the 

 pelvic fins are united behind the cloaca, and there are two 

 stiff grooved copulatory organs, the claspers, which have a 



Fig. 96. PELVIC GIRDLE AND 

 RIGHT PELVIC FIN OF DOGFISH. 



(After Marshall and Hurst.) 



