1 88 Memoir Sears Foundation for Marine Research 



raised; caudal peduncle not greatly expanded laterally, with a precaudal pit above but 

 none below; sides of trunk anterior to anal with longitudinal ridges; snout very short and 

 mouth not widely protrusible; gill openings very large, the 4th and 5th over base of pec- 

 toral; gill arches connected, one with the next, by numerous transverse cartilaginous bars 

 which support soft spongy masses of tissue developed from clumps of modified denticles, 

 the entire gill apparatus forming a sieve of innumerable minute meshes ( i to 2 X 2 to 3 

 mm. in specimen 31 ft. 6 in.) through which water is forced when the mouth is closed, the 

 planktonic food thus being retained and swallowed;' oesophagus lined with large papil- 

 lae, covered with denticles; nostril entirely separate from mouth,^ its anterior margin 

 without barbel; spiracles present; lower eyelid without nictitating fold or membrane; each 

 jaw with a labial fold near the corner; teeth minute, very numerous, many rows func- 

 tional; head of normal shape (not widely expanded); no rostral cartilages; no foramen 

 between mesopterygium and metapterygium of pectoral' (relative number of radials on 

 meta- and mesopterygia not known); heart valves in 2 rows. Development probably 

 ovoviviparous (see p. 192). 



Genera. Rhincodon^ the only known representative of the family, has sometimes been 

 associated with the Orectolobidae (e.g., by Regan*) on the supposition that its nostrils are 

 connected with the mouth by oronasal grooves. Recently, however, it has been found that 

 this is not the case;^ and it is so widely separated from the Orectolobidae in other respects, 

 especially by its complex gill sieve and its lunate caudal with sharply raised axis, that it 

 clearly represents a distinct family. 



Only one genus known, Rhtncodon. 



Genus i?/2/'«coi^o« Smith, 1829 

 Whale Sharks 



Rhlncodon Smith, Zool. J., 4, 1 829: 443; type species, Rhtncodon tyfus Smith. Table Bay, South Africa. 



Generic Synonyms:^ 



Rineodon Muller and Henle, Charlesworth's Mag. Nat. Hist., 2, 1838: 37; no species mentioned/ 



Rhineodon Swainson, Nat. Hist. Fish. Amphib. Rept., r, 1838-1839: 142. 



Rhiniodon Swainson, Nat. Hist. Fish. Amphib. Rept., 2, 1838-1839: 317. 



Rhinodon Muller and Henle, Plagiost., 1841: 77; type species, "Rhinodon tyficus Smith"; evident misquo- 

 tation for Rhtncodon tyfus Smith, 1829. 



Rhineodon Gray, List Fish. Brit. Mus., I, 1857: 66; Rhineodon tyficus Gray, equals Rhtncodon tyfus Smith, 

 1829. 



Micristodus Gill, Proc. Acad. nat. Sci. Philad., 1865: 177; type species, M. functatus Gill. Gulf of California. 



I. For photographs of this gill structure, unique among sharks, see White (Bull. Amer. Mus. nat. Hist., y^, 1937: 



pi. 9, 10) and Gudger (J. Morph., 6S, 1941 : 91-95, fig. 6-8). 

 I. It has been stated repeatedly that the nostril is connected with the mouth by an oronasal groove (for example, 



see Garman, Mem. Harv. Mus. comp. Zool., $6, 1913: 41) ; it has been found recently that such is not the case 



(Barnard, Ann. S. Afr. Mus., jo, 1935: 647, pi. 25). 



3. See White (Bull. Amer. Mus. nat. Hist., 61, 1931: 130) for account of skeletal characters. 



4. Proc. zool. Soc. Lond., 1906: 745. 



5. Most of the generic synonyms here listed are simply emended spellings of Rhtncodon Smith, 1829. 



