378 



COMPARATIVE ANATOMY 



of more or less calcified cartilages, covered by skin and muscles, 

 which are movable upon one another and are derivatives of the 

 fin-rays, and it is provided with a channel along the inner side. 

 These claspers are inserted, in a closed condition, into the cloaca- 

 of the female, and thence into the oviducts ; they are then opened 

 out by means of special muscles, and the seminal fluid flows along 

 their channels into the distended oviducts. In connection with 

 this apparatus there is a gland (p. 18) surrounded by muscular 

 fibres, which is formed as an involution of the integument; in 

 its histological character this calls to mind the uropygial gland of 

 Birds (p. 21). 



In addition to pterygopodia, similar to those of EJasmobranchs 

 the Holocephali possess a pair of curious anterior claspers 

 (Fig. 301), which are protruded from a shallow pouch situated 



2a 



Tio. 301.— Pelvic Arch and Skeleton- of Pelvic Fin and Claspbr of a 

 Male Ghimn'ra monstrota. (After Davidoflf.) Ventral view. 



Pr.il, B, dorsal part of pelvic arch (iliac process) ; S.B, anterior clasper ; a—/, 

 1 — 3, the various segments of the posterior clasper ; Mt, basipterygium ; 

 Ra, JRa^, radii of fin. 



in front of the pelvic fins ; each of these consists of a plate 

 covered with dermal denticles, and in Callorhynchus a grooved 

 structure is present in addition.i There is also a knob-like organ, 

 usually known as the frontal clasper, on the upper surface of °the 

 head. (Fig. 57). 



^ These may correspond to portions of the primitive lateral fin-folds (p. 103) 

 which are not represented in other Craniata. 



