ON JANASSA BITUMINOSA. 351 



specimen there represented; only in ours tlie front or scoop^like 

 cutting-margins of the teeth are buried in the matrix, the view 

 of the specimen being obtained as it were from the oral cavity, 

 while Count Miinster's figure has the front of the teeth exposed 

 as they would be seen had the fish been laid upon its back. 



Another of Mr. Duff's specimens (PI. XI., fig. 1), however, 

 presents the same aspect as that of the figure just referred to, 

 and is almost perfect, rising as that does in bold relief from the 

 matrix in the form of an irregularly rounded cluster, having the 

 peculiar vesicular appearance seen in most of Miinster's figures. 

 This appearance is very remarkable, and at first sight has, as 

 was suggested to us on showing the specimen to a friend, no 

 little resemblance to a cluster of ova-capsules of Fusus antiquus, 

 particularly when the teeth are a little disturbed. 



In connexion with this cluster of teeth a large patch of shag- 

 reen is beautifully displayed, and enables us to determine, in 

 like manner as in the former instance, which is the anterior 

 margin of the specimen, the spreading of the shagreen indicat- 

 ing the direction of the body of the fish. 



In this specimen, as in the first-mentioned, the teeth are divi- 

 sible into two sets, which have their cutting-margins opposed to 

 each other across the transverse median line. Those of the an- 

 terior set belong to the upper jaw, and are closely packed toge- 

 ther and interlocked in the manner previously described, in four 

 transverse or horizontal rows : the remains of a fifth row are 

 distinctly visible. The arrangement is the same as in the first- 

 described specimen : that is, in each row there is a central tooth 

 with three lateral ones on each side, the extreme flanking tooth 

 on either hand being petalodontoid in form ; and the teeth com- 

 posing the row next the transverse median line are the largest, 

 whUe those in front, or those in the lower supporting rows, be- 

 come 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 upper jaw, whose cutting-margins are turned back- 

 wards. In the lower jaw four horizontal rows are distinctly 



