324 Messrs. Hancock & Atthey on the Generic Identity 



agree in a remarkable manner with those in Myliohatis aquila 

 and Zygobatis marginata — a relationship which was recog- 

 nized \)j Agassiz*. In the extraordinary dental apparatus of 

 these two interesting forms the teeth or plates are placed 

 crosswise on the anterior portion of the jaws in rows succeed- 

 ing each other from back to front. The largest primary tooth 

 is median : on each side of it there are two other primary 

 teeth, both of which are small in the first genus, and only one 

 in the second ; all these teeth are charcterized by having six 

 sides ; and each row is flanked by a small or secondary tooth, 

 distinguished by having only five sides. Thus it appears that 

 each transverse row is composed of seven teeth, five of which 

 may be looked upon as primary, two as secondary, arranged 

 exactly as the teeth are in Janassa, and agreeing with them 

 exactly in number. 



Now it cannot be doubted that the disposition of the teeth 

 is the same in Glimaxodus as it is in Janassa ; and in fact the 

 specimens of the former, on the slab previously mentioned, 

 verify this assertion when aided by the light derived from the 

 latter. Alone perhaps these specimens might have justified 

 the inference ; but taken in connexion with what is known re- 

 specting Janassa^ there can now be no hesitation upon the 

 subject. Indeed the large, symmetrical, central teeth of two 

 rows lie in proper order one over the other ; and in contact 

 with the upper one, and side by side with it, is the first lateral 

 tooth in its exact true position ; and a little further away, but 

 almost touching it, is a secondary tooth, apparently belonging 

 to this side. Overlying the first, lateral, primary tooth in 

 front are the distorted remains of what seems to be the second 

 lateral tooth. On the other side of the central tooth, and some 

 little distance from it, is another primary tooth, which, from 

 its oblique form, is undoubtedly the second lateral tooth of 

 this side : it lies in juxtaposition to its flanking Petalodontoid 

 tooth. All these teeth, with the exception of that last named, 

 lie with their crowns uppermost, and belong to one row ; the 

 central tooth and the three lateral teeth of one side are all 

 present, and lie nearly in their natural order ; and the second 

 lateral tooth and the secondary tooth of the other side are not 

 far removed from their right position. So here we see a whole 

 row of seven teeth complete, with the exception of one of the 

 first lateral teeth. Two other small lateral teeth are on the 

 same slab, and rest with their faces downwards, or in the 

 opposite direction to those already spoken of. These belong 

 apparently to the opposing jaw, and both lie in contact with 

 the large central teeth ; and one of them, as an opposing tooth, 

 * Poissons Fossiles, tome iii. p. 375. 



