58 Messrs. Hancock & Howse on Janassa bituminosa 



flanking tooth on cither hand being pekilodontoid in lorni ; 

 and the teetli coinposini;- tiic row next the transverse median 

 line are tiie hirgest, while those in front, or those in the lower 

 sujiporting rows, become gradually smaller. 



The teeth of the lower jaw, or those at the posterior margin 

 of the cluster, are in a comparatively disturbed state ; but the 

 anterior cutting-margins are turned forward, so as to oppose 

 those of the uj)])er jaw^, whose cutting-margins are turned 

 backwards. In the lower jaw four horizontal rows are dis- 

 tinctly determinable, while indications of a fifth can be traced. 

 On account of the disturbance of these teeth, the central large 

 teeth of four rows are well displayed in profile, being turned 

 over towards the right of the observer, and lying in regular 

 order, one behind the other, so that the whole length of the 

 teeth is exposed, the roots being traceable in the matrix. 

 Several of the lateral teeth are scattered on either side, and 

 three or four are removed to some distance to the left. 



This specimen is fortunately broken through transversely 

 near the centre, in such a manner that the greater portion of 

 the upper or crushing-disks, with the anterior cutting-margins 

 of one row of teeth and the backs or under-surfaces of another, 

 are finely dis})layed. And thus we obtain a clear demonstra- 

 tion of the arrangement of the teeth in this fine specimen, and 

 at the same time a complete exposition of the characters of the 

 teeth themselves. 



A third slab exhibits a dense mass of teeth of an irregularly 

 rounded form, comprising numerous teeth of both jaws (PI. III. 

 fig. 2). Here, again, the shagreen shows the position in which 

 the body of the fish was deposited ; but as all the teeth have 

 the anterior scoop-like cutting-margins in one direction, there 

 can be no question as to which is front. The specimen rests 

 on the slab with the face uppermost, much as in the last case; 

 only the Avhole are turned forward, and, unlike it, the teeth 

 are in a much disturbed state, particularly those of the under 

 jaw, Avliich lie uppermost. These, or at least all that remain 

 of them, have been pushed so far forward that they overlie 

 those of the u])per jaw towards the left side, leaving exposed 

 the u])})er surface of the large central tooth and the first lateral 

 of the WTirking row of the up])er jaw, Avhich are well exhibited 

 in their true position ; and the remains of a second lateral tooth 

 and one or two of the ])etalodontoid form are seen at the ex- 

 treme right. These exposed teeth of the u])])er jaw have their 

 crushing-disks and cutting-margins turned u])wards; and their 

 roots are well displayed, siiiking backwards into the matrix. 

 The few teetli of the under jaw already spoken of on the left 

 have their under surfaces or backs exposed, 1 he crushing-disks 



