1 5 6 



SELACHII 



and not visible from above. The skeleton preserves many of its 

 shark-like characters, and in all essentials resembles that of the 

 Squaliformes. 



Family SQUATINIDAE. The body and head are considerably depressed, 

 but the tail is still powerfully developed (Fig. 116). It has lateral keels. 



A. 



FIG. 119. 



A, occipital region of the skull of Raja from behind. B, skull and anterior portion of 

 pectoral-fin skeleton of Trygon tuberculata, Lac., ventral view. (Both after Gegenbaur.) ax, 

 anterior axis of fin ; 5, basihyal ; c, occipital condyle ; cf, nasal flap ; e, endolymphatic foramen ; 

 l.c, lateral condyle ; LI, foramen for lateral-line canal ; m.k, Meckel's cartilage ; p.q, palato- 

 qnadrate ; r, vestigial rostrum ; rd, radial ; vg, vagus foramen. 



The mouth is very far forward, there being no rostrum. The teeth are 

 small and conical. The anterior vertebrae may be slightly modified, but 

 not fused. The centra are typically tectospondylous (Fig. 52). Neural 

 spines are well represented (Fig. 52). In the form of the palato- 

 quadrate cartilage, with its powerful palato-basal process, of the hyoid 

 arch, and of the pectoral girdle, the Squatinidae differ from the next 

 Division, and resemble the Squaliformes. Obviously they are more 

 closely related to the latter than to the Scyllioidei. In the structure oi 



