Fishes of the Western North Atlantic 95 



Suborder HETERODONTOIDEA 



Characters. Anal fin present 5 2 dorsal fins with well developed spines; only 5 gill 

 openings, the last 3 or 4 over base of pectoral j snout not beak-like, without lateral teeth 

 or cirri; teeth similar in both jaws, those toward center of mouth smaller, with 3 to 5 

 cusps,* but those along outer parts of jaws much larger, rounded (molar), without cusps, 

 several rows functional; midtrunk subcylindrical (shark-like), but head with snout 

 strongly flattened both above and below; tail sector flattened below; anterior margins of 

 pectorals not expanded forward beyond ist gill opening; nostrils connected with mouth 

 by a deep groove; eye without nictitating fold or membrane; spiracles present; inner mar- 

 gins of pelvics entirely separate, posterior to cloaca; vertebral column completely seg- 

 mented throughout its length, its axial canal much contracted in the region of the centra, 

 which are fully differentiated, and notochord greatly constricted segmentally in centra; 

 vertebral centra with internal calcareous lamellae radiating from a central ring; skull 

 without antorbital processes or separate antorbital bars; upper jaw (palatoquadrate carti- 

 lage) attached by a short ligament to hyomandibular arch as well as closely and much more 

 extensively to sides of preorbital region of cranium;" rostral cartilage lacking; neural 

 spines not attached to dorsals; propterygial cartilage of pectoral bears i radial element; 

 heart valves in only 2 rows; claspers of males projecting freely from pelvics, their axial 

 cartilages with 3 movable accessory cartilages at tip and attached to basipterygium of the 

 fin by 2 small connecting elements. Development oviparous; egg cases horny with spiral 

 flanges, but without tendrils. 



Families and Genera. Only one modern family (Heterodontidae) and genus {Met- 

 er odontus Blainville, 1 8 1 6) with the characters of the suborder.* 



Range. East Africa, East Indies, New Zealand, Australia, China, Japan and eastern 

 Pacific north as well as south; not known in Atlantic or Mediterranean. 



Fossil Teeth. Upper Jurassic to Pliocene in Europe; Upper Cretaceous to Eocene in 

 Africa; Miocene in South America, New Zealand, Australia. 



Suborder GALE OWE A 



Characters. Anal fin present; 2 (rarely i) dorsal fins, without spines; only 5 gill 

 openings with rudimentary 6th arch; snout not beak-like, without lateral teeth or cirri; 

 teeth of essentially the same type in front of mouth as near corners; trunk subcylindrical, 

 not strongly depressed; eyes lateral; anterior edges of pectorals not extending forward 

 past 1st gill openings; nostril either connected with mouth or separate from it; nictitating 

 membrane and spiracles present or absent; inner margins of pelvics either separate posterior 

 to cloaca, or more or less united; vertebral column completely segmented throughout its 

 length, its axial canal much contracted or obsolete in regions of centra, the latter being fully 

 differentiated; notochord greatly constricted segmentally in centra, or even completely 

 obliterated there, but dilated in spaces between concave faces of adjoining vertebral centra; 



4. Cusps may be entirely worn off in large specimens. 5. Firmly articulated there in fossil forms. 



6. See Fowler (Bull. U.S. nat. Mus., 100 [x^], 1941 : 15) for list of generic synonyms. 



