COMPAGNO and SPRINGER: NEW GENL'S OF CARCHARHINID SHARKS 



Origin of first dorsal fin far forward, varying 

 in position from above fourth gill opening to 

 slightly before pectoral axilla; midpoint of first 

 dorsal base much closer to pectoral axilla than 

 to pelvic origins; free rear tip of first dorsal 

 anterior to pelvic fin origins. 



Second dorsal nearly as large as first, its height 

 about 70 '"r of first dorsal height; its posterior 

 margin strongly concave. 



Anal smaller than second dorsal, slightly more 

 than half its height, its base about % of second 

 dorsal base length; its posterior margin nearly 

 straight or shallowly concave; its origin poster- 

 ior to second dorsal origin by about i/-) to \A of 

 second dorsal base length; posterior ends of sec- 

 ond dorsal and anal bases opposite. 



Caudal without projecting ventral lobe-tip in 

 adults, preventral margin slightly more than I/3 

 of dorsal margin length; subterminal margin 

 long, over half length of terminal margin ; cau- 

 dal dorsal margin length about i/o of total 

 length; terminal sector of caudal about 1/3 of 

 dorsal margin length; vertebral axis of caudal 

 only slightly raised above body axis. 



Figure 5. — lago omanensis. A. Ventral aspect of trunk 

 of mature male to show size and position of clasper 

 siphons. B. Dorsal surface of left clasper. C. Partially 

 expanded tip of left clasper. AP, apopyle ; C, connection 

 between rhipidion and cover rhipidion; CR, cover rhipi- 

 dion; EG, epirhipidial groove; ER, exorhipidion; HP, 

 hypopyle; P-2, pelvic fin; ESA, pseudoperal aperture; 

 ESP, pseudopera; PSP, pseudosiphon pouch; R, rhipi- 

 dion; S, siphon sac; SG, subrhipidial groove. 



Vertebrae moderately numerous, 129 to 147 

 in total count {N = 16). Monospondylous pre- 

 caudal (MP) centra 24.5 to 27.6 ^r of total count; 

 diplospondylous precaudal (DP) centra 33.6 to 

 36.1; and diplospondylous caudal (DC) centra 

 37.2 to 40.1 (N =8). A ratios 120 to 162, B 

 ratios 102 to 137 (N = 11 ) . DP and DC centra 

 more numerous than MP centra and nearly equal 

 to each other, DP MP ratio 1.22 to 1.46 and 

 DC/MP ratio 1.38 to 1.63 (/V = 8). Transition 

 between MP and DP centra easily delimited on 

 radiographs, over pelvic region. Posteriormost 

 MP centra not greatly hypertrophied. DP cen- 

 tra of relatively uniform length throughout, not 

 forming a stutter zone of alternating long and 

 short centra. 



Vertebral calcification pattern a modified ver- 

 sion of White's (1937) "Maltese cross" pattern, 

 without diagonal calcified lamellae; notochordal 

 canal unusually large (Figure 3C); wedgelike 

 intermedialia strongly developed. 



Supraorbital crest of cranium strongly devel- 

 oped and entire. 



Intestinal valve of spiral type, with about five 

 turns. 



lago is apparently livebearing (see section in 

 Reproduction below) , but whether or not a yolk- 

 sac placenta is formed cannot be determined 

 from available specimens. 



lago omanensis (NORMAN, 1939) 



Eugaleus omanensis Norman, 1939, p. 11, Fig. 

 3 (type-locality. Gulf of Oman); Compagno, 

 1970 (generic systematics) . 



Galeorhinus omanensis Misra, 1949, p. 21 (in 

 list of Indian elasmobranchs, name only) ; Fowl- 

 er, 1956, p. 17 (description, after Norman); 

 1967, p. 363 (in list of fishes of the world, name 

 only). 



MATERIAL 



Seven males, 224 to 365 mm; nine females, 

 358 to 582 mm (Table 1); holotype, British 

 Museum (Natural History) Reg. No. 1939.5.24.9, 

 a 280-mm female from Gulf of Oman. Speci- 



619 



