244 FOSSIL REMAINS OF HYBODUS 



cal studs, each of which is attached by a neck to a round and 

 expanded base, (fig. 5, b & c). The surface of these dermal 

 points is marked with very prominent cost<e, and their sub- 

 stance appears to be exactly analogous to that of the teeth. 

 The portion of the skin of Acrodus, an allied genus, figured 

 in Dr. Buckland's Bridgewater Treatise, seems to present a 

 closely analogous character. 



Notwithstanding that the teeth in this specimen are very 

 numerous, and for the most part implanted in the bone by their 

 original attachments, I have been quite unable to form an idea 

 respecting the character which the entire jaws would present, 

 and the relations which they have borne to the surrounding 

 parts. The fragments of jaws figured by Agassiz, throw no 

 light upon this matter ; and although in the ' Poissons Fos- 

 sils ' a great many species are characterised by the osseous 

 spines, and the genus often alluded to in the remarks upon 

 Ichthyodorulites, the complete history of its characters and 

 probable affinities has as yet been postponed. l 



I am not able to determine whether the two fragments fi- 

 gured belong to one and the same side of the mouth, or to 

 the upper and lower jaws : there is nothing like a symphysis, 

 nor at the termination of the rows do the teeth present any 

 decided diminution in size or number, by which the position 

 of the lateral ligamental articulations might be detected. — 

 The series of teeth on the larger fragment consists of seven 

 rows, six deep, disposed along the anterior border of the 

 mass ; at one extremity the continuity of the series being in- 

 terrupted by the fractured lateral edge or border of the mass 

 itself, the rows of teeth are continued nearly to the margin of 

 the opposite lateral border, but here they make a sudden bend 

 inwards and backwards, by which their continuity is pre- 

 served ; the portion so recurved consists of five additional 

 rows, and its termination about the centre of the mass is 

 shown in the figure. Reasoning from the analogy of the 

 jaws in the existing genera of sharks, and also from the ap- 

 parently forcible displacement of the teeth at the immediate 

 spot where the bend occurs, this sudden curve would appear 

 to be the result of accident, rather than the natural disposi- 

 tion of the parts. The smaller fragment however exhibits a 

 very similar and equally sudden alteration in the direction of 

 the rows of teeth, and the same thing may be observed in the 

 original jaw figured by M. de la Beche in the ? Geological 

 Transactions.' 



I I "believe the 12th livraison of the ' Poissons Fossils' is very shortly ex- 

 pected, and it may possibly contain the history of the genus Hybodus. 



