578 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 115 



Sexual dimorpMsm: There is a striking difference in dentition of 

 adult males as compared with females or juvenile males (fig. 3). In 

 adult males the cusps of the teeth are long and slender and the middle 

 and posterior teeth of each side of the lower jaw are erect. The 

 anterior teeth are greatly elongate and flexuous and somewhat round 

 in cross section. Several rows of the anterior lower teeth in the adult 

 male appear to be functional. Sexual dimorphism of dentition in 

 sharks has been reported only for the squalid genus Deania (see 

 Bigelow and Schroeder, 1957, and Garrick, 1960). Dental sexual 

 dimorphism also exists in Rhizoprionodon lalandei, R. oligolinx, and 

 probably R. taylori; it also exists to a much lesser degree in Loxodon. 

 The phenomenon is probably widespread and unrecognized in sharks. 

 Physodon is based on an adult male S. laticaudus and the type descrip- 

 tion of iS'. laticaudus is based on an adult female. 



This species is free-living at sizes of at least 126 mm. t.l. (130-150 

 mm. according to Setna and Sarangdhar, 1949). Maximum size in 

 Indian waters is about 26 inches (approximately 660 mm.). Breeding 

 occurs all year with peak parturition from November through January. 

 Up to 12 embryos occur per uterus, but usually no more than 14 young 

 per female. Mature eggs are small, about one mm. in diameter 

 (Setna and Sarangdhar, 1949). 



Thillayampalam (1928) has given a detailed anatomical description 

 of S. laticaudus (as Scoliodon sorrakowa) . Some portions of the work 

 are based on other species {Rhizoprionodon), but the study is an 

 important one. 



Distribution (see "Material"). — This is a common species and its 

 absence from Australia, the Philippines, the Celebes, Moluccas, 

 New Guinea, and Oceania I believe to be real. The distribution seems 

 to indicate that the species is essentially a continen tally restricted one, 

 able to traverse only the narrowest passes between coastlines. Setna 

 and Sarangdhar (1949) reported that the species (as S. sorrakowa) 

 lived in rocky areas up to three miles offshore in Bombay waters. 



NoMENCLATURAL DISCUSSION. — As mentioned above, Physodon 

 mulleri was based on an adult male of S. laticaudus. Its dentition is 

 markedly different from that of the female upon which Miiller and 

 Henle's description of C. (S.) laticaudus was based. There are adult 

 males in the syntypic series of S. laticaudus but undoubtedly these were 

 not examined for dentition. This is indicated by the fact that, in the 

 first pair of pages 27 and 28 in Miiller and Henle's Plagiostomen (see 

 discussion on page 573), the description of C. (S.) laticaudus is of a 

 single stuffed female specimen in the Berlin Museum. In the second 

 pair of pages 27 and 28, additional material (including alcohol- 

 preserved specimens) is listed, but the description is identical with the 

 previous one. 



