184 



PLEURACANTHOD1I 



.ar 



FIG. 149. 



Pelvic girdle of Plcuracanthus 

 Gaudryi, Brogn. (From Quart. 

 Journ. Micr. 6'ci.) 



FIG. 150. 



Ventral view of the pelvic girdle and 

 right fin of a female Pleuracanthus Oclbcr- 

 gensis, Fr. a, jointed axis ; p, pelvic carti- 

 lage ; pr.r, preaxial radial; pt.r, postaxial 

 radial. (After Fritsch, from Quart. Journ. 

 Micr. Sci.) 



FIG. 151. 



Pelvic girdle and fin- 

 skeleton of a male Pleiiracan- 

 thus Oelbergcnsis, Fr. (After 

 Fritsch.) a.r, anterior preaxial 

 radial resting on girdle ; bp, 

 segmented basipterygial axis ; 

 cl, modified radials of clasper ; 

 p, pel vie girdle (left half) ; p.r, 

 preaxial radials. 



Sub-Class 3. CLADOSELACHII. 



The extinct family Cladoselachidae contains some of the earliest 

 and most interesting of the fossil Chondrichthyes. Isolated sharp- 

 cusped teeth have long been known, under the name Cladodus, 

 from Devonian and Lower Carboniferous strata ; but it is only latel 

 that more or less complete fossils have been found (Newberry [309 

 Dean [102, 104]). 



In general shape Cladoselaclie resembles a Notidanid except 

 that the tail ends in a sharply upturned tip (Fig. 152). The 

 caudal fin has a large ventral lobe. Horizontal keels extend along 



