46 



Memoir Sears Foundation for Marine Research 



Family RHINOBJTIDAE 



Characters.^'' Body sector of trunk ranging from moderately flattened, with wedge- 

 shaped snout and tail sector not marked off from body, to strongly flattened and broadly 

 rounded anteriorly in disc-like form, with tail sector more or less clearly marked off 

 though moderately stout. Snout not produced as a blade, its edges without teeth. Anterior 

 pectoral rays extending forward only a little past level of nostrils in some but to level 

 of end of snout in others; posterior corners of pectorals extending rearward at least 

 as far as origins of pelvics. Origin of first dorsal considerably posterior to rear tips of 



Figure 8. Rhinobatos Untiginosus, from off Useppa Island, 

 Florida (Harv. Mus. Comp. ZooL, No. 35856). Gill arch 

 (above) and side view of gill fold (below), about 2.8 x. 



pelvics. Caudal without definite lower lobe, its posterior contour straight or convex, 

 its corners rounded; caudal axis not raised, or only very slightly so (Fig. 14 D; 18B). 

 Eyes with or without rounded velum above pupil, the orbit outlined below and anteriorly 

 by a deep groove in some species (as in the Rhynchobatidae) but only faintly so, if at 

 all, in others. Spiracles immediately behind eyes, either transverse or slightly oblique, 

 with inner ends directed rearward (as in Rhynchobatidae), their posterior margins with 

 or without transverse folds. Rostral projection extending to tip of snout, or not. Anterior 

 and posterior surfaces of gill arches, inward from gill filaments, each with a series of 

 low, firm, widely-spaced knobs (Fig. 8). 



Development is ovoviviparous in the great majority, but perhaps oviparous in 



10. For account of the head skeleton and a comparison with other batoids, see Holmgren (Acta Zool. Stockh., 22, 

 1941: 52, 64). 



