Fishes of the Western North Atlantic i 5 



3 b. Tail sector slender, extremely so In many cases, and sharply marked 

 off from body sector; dorsal and caudal fins, if any, not supported dis- 

 tally by horny rays. 



4a. Pelvis with prepelvic spur at outer corners; outer margin of pelvics 

 concave in most; spiracles with traces of gill folds. Rajoidea. p. 132. 

 4b. Pelvis without spur at outer corners; outer margin of pelvics straight 

 or convex; spiracles without trace of gill folds. 



Myliobatoidea, p. 331. 



Sequence of Presentation. The batoids as a whole constitute a highly specialized 

 group, and the divergences between their major subdivisions represent still further 

 specializations In one direction or another beyond their common divergence from the 

 more generalized elasmobranch stem, as represented by the Sharks. Consequently It 

 is not possible to represent the mutual interrelationships between the several suborders 

 by any arrangement of them in linear series. Of the batoids, the Sawfishes (Pristoidea) 

 are the most nearly shark-like in form of body; also, their fins, paired as well as un- 

 paired, have horny rays (ceratotrichia) in addition to cartilaginous radlals, as do the fins 

 of Sharks. Although the saw of the Sawfish represents extreme specialization in one 

 direction, this is almost exactly paralleled in the Saw Sharks (Pristiophoroldea). We, 

 therefore, follow common usage In commencing this account with the Pristoidea, 

 leading to the Rhinobatoidea. Also, it is customary to place the Myliobatoidea after 

 the Rajoidea since they represent the extreme development of batoid specialization In 

 general, and nothing would be gained by doing otherwise. Although the Electric Rays 

 have been placed between the rhinobatoids and the rajoids,^' between the rajoids and 

 the myliobatoids,-^ or after the myliobatolds,^'' we place them immediately after the 

 rhinobatoids, thinking their well developed unpaired fins, with horny rays in addition 

 to the cartilaginous radlals, more significant from the standpoint of relationships than 

 the extreme specialization of their electric organs or the great development of their 

 antorbltal cartilages. 



Suborder PRISTOIDEA 

 Sawfishes 



Characters. General form more shark-like than ray- or skate-like, but with trunk 

 and head flattened ventrally; the head especially flattened, its anterior part so strongly 

 depressed as to be very thin dorsoventrally. No evident demarkatlon between body 

 and tail sectors of trunk (Fig. 2). Snout extended as a long narrow flattened blade 

 (the so-called "saw") armed along either edge with a single series of transverse teeth 



27. See especially Garman (Mem. Harv. Mus. comp. Zool., 36, 1913: 257), Rey (Fauna Iberica, Feces, i, 1928: 515), 

 and Fowler (Bull. U. S. nat. Mus., 100 [13], 1941: 332)- 



28. Jordan, Evermann and Clark, Rep. U. S. Comm. Fish. (1928), 2, 1930: 27; Benin, Bull. Inst, oceanogr. Monaco, 



775' 1939- 



29. Berg, Classification of Fishes, Trav. Inst. Zool. Acad. Sci. URSS, 5 (2), 1940, and lithoprinted ed. 1947: 139 (Russ.), 

 381 (Eng.); Romer, Vert. Palaeont., 2nd ed., 1945: 577. 



