THE STATE GEOLOGIST. 



73 



Genus S^mionotus Agassiz. 



Trunk fusiform. Marginal teeth slender, conical, somewhat 

 spaced, inner teeth stouter; opercular apparatus well-developed, 

 with a narrow arched preoperculum. Ribs ossified. Fulcra un- 

 usually large. Paired fins small, dorsal fin large, arising at or 

 behind the middle of the back, and in part opposed to the 

 relatively small anal; caudal fin slightly forked. Scales smooth 

 or feebly ornamented, and the narrow overlapped margin pro- 

 duced at the angles and at the superior border. Flank-scales 

 not more than twice as deep as broad, the dorsal ridge-series of 

 acuminate scales forming a prominent crest. — (Woodward.) 



The cranial osteology of this genus is imperfectly known, a 

 consequence of the inferior preservation of most of the remains. 

 Agassiz, in his great work on Fossil Fishes, described briefly 

 the arrangement of cranial plates in 5*. nilssoni, and more recently 

 E. Schellwien has furnished us with similar information regard- 



pm<--- 



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Fig. o. 



Semionotus capensis Woodw. Lateral aspect of head, X Yi. br, branchi- 

 ostegal rays; cl, clavicle; co, circumorbitals ; cor, coracoid (?); fr, frontal; 

 *. op, interoperculum ; md, mandible ; mx, maxilla ; pa, parietal ; p. cl, post- 

 clavicular scale ; p. 0, postorbital ; p. op, preoperculum ; p. t, post-temporal ; 

 s. cl, supraclavicle; so, suborbitals; s. op, suboperculum; sq, squamosal; s. t, 

 supratemporal. Sensory canals are indicated by dotted lines ; doubtful sutures 

 by dashes (after Schellwien). 



ing S. capensis f Fig. 9), both of these forms being trans- Atlantic 

 species. Newberry remarks in his Monograph on Triassic Fishes 

 that he has "not been able to verify by personal examination 



