COMPAGNO and SPRINGER: NEW GENUS OF CARCHARHINID SHARKS 



First dorsal fin triangular with height much 

 less than length from origin to free rear tip; 

 origin ill-defined, grading into predorsal ridge; 

 anterior margin slightly concave basally but con- 

 vex towards fin apex, with a 45 degree slope 

 relative to body axis; apex acutely rounded, 

 posterior margin somewhat concave, free rear 

 tip slender, elongate, acute; base much longer 

 than fin height, inner margin about 60 to 70% 

 of fin height; end of first dorsal base about 

 over adpressed apex of pectoral; pectoral free 

 rear tip anterior to pelvic origins by a distance 

 nearly or quite equal to lengths of pelvic bases. 



Second dorsal fin generally similar in shape 

 to first dorsal; its height about half length from 

 origin to free rear tip; fin base about 1.4 to 1.5 

 times height; inner margin about 0.5 to 0.7 of 

 height; origin of second dorsal posterior to mid- 

 point between anal origin and posterior end of 

 pelvic base; free rear tip of second dorsal op- 

 posite or slightly posterior to that of anal; sec- 

 ond dorsal over twice area of anal. 



Anal fin a low triangle, with height about 0.4 

 in length, anterior margin broadly convex, apex 

 rounded, posterior margin moderately concave, 

 free rear tip slender and acute, and inner margin 

 concave; inner margin almost or quite equal in 

 length to height; fin base 1.4 to 1.6 times fin 

 height. 



Dorsal margin of caudal nearly straight, pre- 

 ventral margin broadly convex, and junction of 

 preventral and postventral margins rounded; 

 postventi-al margin long, concave anteriorly but 

 nearly straight posteriorly and curving abruptly 

 upward into subterminal notch; subterminal 

 margin nearly straight, terminal margin invar- 

 iably frayed but apparently moderately concave. 



Vertebral counts given in Table 3. 



Vertebral calcification pattern was studied 

 from transverse sections and radiographs of 

 centra from below first dorsal fin. Terminology 

 for vertebral parts follows Ridewood (1921). 

 Primary double cone without diagonal calcified 

 lamellae; solid dorsal, lateral, and ventral inter- 

 medialia present, separated by uncalcified areas 

 for the basidorsals and basiventrals (Figure 

 3C) ; notochordal canal at constricted portion of 

 double cone unusually large (as in many other 



deepwater sharks, a feature possibly correlated 

 with habitat). 



The chondrocranium was dissected out in one 

 specimen but is not described here. It is similar 

 in structure to the crania of Galeorhiniis and 

 Mustelus described by Gegenbaur (1872) but 

 differs in numerous details from both. 



Stomach very large, subdivided into a sack- 

 like fundus and a long slender pylorus. The 

 fundus extends posteriorly over two-thirds the 

 length of pleuroperitoneal cavity, then reverses 

 direction as the pylorus to continue anteriorly 

 nearly to root of liver, where it joins the spiral 

 intestine. The latter is fusiform, with a spiral 

 valve of about five turns (Figure 3D). The nar- 

 row rectum has a slender rectal gland attached 

 distally to the epigonal organ in both sexes. 

 Liver only moderately large, with paired lat- 

 eral lobes concealing small medial lobe, posterior 

 ends of lateral lobes extending only one-half to 

 two-thirds of distance to posterior end of pleuro- 

 peritoneal cavity. Spleen elongate, not nodular, 

 originating dorsally on distal end of fundus and 

 coursing anteroventrally on pylorus to spiral in- 

 testine, where it extends posteroventrally to be- 

 low the first intestinal valve. Pancreas elongate, 



Table 3. — Vertebral numbers in male and female lago 

 omanensis. 



single, located anterior to spiral intestine and 

 dorsal to stomach. Ovaries well-developed only 

 on right side, with long epigonal organ extending 

 posteriorly to rectal gland; both oviducts well-de- 



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