276 PALEONTOLOGY OF ILLINOIS. 



Cladodtjs Fullebi, St. J. aud W. 



PL IV, Fig. 9. 



Mr. L. A. Fuller has discovered in tlie sbalein connection with coal 

 No. 31 at Bloomington, Illinois, a remarkable specimen which exhibits 

 no less than the entire jaws of a fish whose dentition proclaims its 

 affinities with the genus Cladodus. The cartilages of the jaws, though 

 somewhat crushed and flattened, are quite distinct in their general out- 

 line, and would at first glance be pronounced as those belonging to a 

 Plagiostome, in general shape bearing a striking resemblance to the 

 jaws of the Squall, as illustrated in the genus Odontaspis of the existing 

 seas. The rami of the lower jaw are characterized by their great depth 

 in the region posterior to the middle, and apparently broadly rounded 

 to the articular extremity ; the rami of the upper jaws are somewhat 

 crowded forward, vertically narrower and more produced in front. The 

 rami of both the upper and lower jaws appear to have been somewhat 

 thickened in the dentigerous region, and very thin in the opposite bor- 

 ders, with indications of the longitudinal folds, the anterior protuber- 

 ances and the posterior shallow excavations, while the structure is 

 unmistakably that of semiosseous cartilage, in all which particulars it 

 closely agrees with the jaw cartilages of the more modern order of 

 Selachians. The greatest length of the jaw is about 11 inches, greatest 

 vertical depth of the rami of the lower jaw 2.5 inches, that of the upper 

 rami probably less than 2 inches. 



The teeth are evidently displaced, as appears from the very irregular 

 arrangement, or, indeed, apparent want of order in their present dispo- 

 sition, beiug collected in a disordered group between the anterior 

 extremities aud extending backward three-fourths the distance to the 

 articular extremities. So far as it is possible to determine, there would 

 seem to be less diversity iu form than occurs in Odontaspis, the arrange- 

 ment being the same, or apparently iu serial rows from within outward. 

 The largest individuals exposed are considerably less than half an inch 

 " iu hight, and about the same in lateral extent of base. Individually, 

 the teeth are symmetrical in shape, base strong, gently sinuous in front 

 broadly rouuded posteriorly, the inferior surface moderately excavated ; 

 the auterior marginal border relatively narrow, broadly arched inward 

 between the anterolateral shoulders, which are moderately produced 

 and between which the border is very gently arched downward ; the 

 postero-superior surface of the base is unknown. The crown consists 

 of a strong, moderately tapering, trenchant median cusp, which is com- 

 pressed or gently arched in front and slightly excavated towards the 

 base, broadly rounded behind, with a slight sigmoidal curvature from 

 base to apex, and ornamented in either face with exceedingly delicate 



