FISHERY BULLETIN: VOL, 69, NO. 3 



Mouth opening subtriangular, broad, 2 to 214 

 times as wide as long ; labial furrows extending 

 around mouth corners, the upper furrows longer, 

 extending anteriorly only to below eye pupils; 

 large papillae absent from buccal cavity. 



Teeth small (Figures 3A and 4), largest with 

 greatest width at root about 1.5 mm in 457-mm 

 female; tooth rows 46 to 55/37 to 45; 2 to 3 

 series functional along edges of jaws; teeth 

 in mixed alternate and imbricate overlap pattern 

 of Strasburg (1963); no serrations; premedial 

 edge of crown in anteroposteriors convex, post- 

 lateral edge deeply notched forming a low post- 

 lateral blade on crown foot; all teeth with a 

 strong basal ledge and groove, transverse ridges 

 on crown foot; roots low, deep, with transverse 



Figure 3. — lago omanensis. A. Typical teeth: upper, 

 buccal surface ; lower, labial surface. B. Eye. C. Cross 

 section of trunk vertebra; thoroughly calcified areas 

 shown in black. D. Valvular intestine, one side cut away. 

 Drawing by L. J. V. Compagno. 



groove on attachment surface but transverse 

 notch weak; teeth not noticeably protruding 

 when mouth is closed. 



Dignathic heterodonty very weak, with upper 

 anteroposteriors having slightly higher crowns 

 than lower ones; disjunct monognathic heter- 

 odonty indicated by differentiation of medials 

 in one row on upper jaw and about 3 in lower; 

 medials smaller, with erect primary cusps, large 

 premedial and postlateral blades, and no cusi^Iets; 

 larger anteroposteriors are sharji-edged, com- 

 pressed, bladelike cutting teeth witli an oblique 



Figure 4. — lago omanensis. Teeth of right side of upper 

 and lower jaws; labial aspect. Dotted lines indicate 

 jaw symphysis. 



primary cusp and no cusplets; anteroposteriors 

 show moderate gradient monogrnathic hetero- 

 donty, with teeth becoming smaller, more 

 oblique-cusped, and lower-crowned towards ends 

 of dental band ; posteriormost teeth with strong 

 primary cusps; ontogenic heterodonty not known 

 at present; gj'nandric heterodonty indicated 

 only by slightly more erect cusp tips on antero- 

 posteriors of adult males. 



Trunk not markedly compressed, less than 

 twice as high as wide, subtriangular in cross 

 section; a low interdorsal ridge present; lateral 

 dermal keels and precaudal pits absent from 

 caudal peduncle. 



Dermal denticles of trunk below first dorsal 

 longer than wide, crown with a high, narrow 

 ridge extending to tip of posteriorly directed 

 cusp; a pair of lateral ridges weakly developed 

 or absent, lateral cusps weak or absent. 



Pectoral fins larger than first dorsal fin in 

 area, their anterior margins about 11,4 times as 

 long as combined base and inner margin lengths; 

 distal tip of adpressed pectoral about over its 

 free rear tip when pectoral inner margin is held 

 parallel to body axis; origin of pectoral below 

 or slightly in advance of fourth gill opening; 

 pectoral skeleton projecting less than halfway 

 into fin, its longest distal radials about equal 

 in length to corresponding proximal ones; distal 

 radials with truncate tips and parallel edges. 



Pelvic anterior margins less than half length 

 of pectoral anterior margins; pelvic bases equi- 

 distant between first and second dorsal bases. 



Claspers with pseudoperae, pseudosiphons, 

 cover rhipidia, true rhipidia, and exorhipidia 

 (Figures 5B and 5C) ; siphon sacs large, extend- 

 ing anteriorly to level of pectoral free rear tips 

 (Figure 5A); margins of clasper cartilage 

 rolled, with margins overlapping to form a tube; 

 clasper hooks absent. 



618 



