LEPIDOIDS. 69 



earliest of those in which palaeontologists have recognized the traces 

 of animal life, the same peculiarities are manifested in the structure 

 and disposition of their dental organs, as in those of many of 

 the existing osseous fishes. The teeth are always present on the 

 palatine bones, and are arranged in several rows on the alveolar 

 margins of the intermaxillary and premandibular bones ; those of the 

 outer row are the largest, and are sometimes in the form of obtuse 

 cones ; the posterior ones are small, simple and close-set, like the 

 bristles of a brush. 



In the genus Amhlypterus all the teeth are of the latter kind, and 

 their minute slender character is the more remarkable on account of 

 the disproportionate magnitude of jaws. In the genera Palceoniscus 

 and Semionotus, the maxillary teeth also resemble a fine brush ; indi- 

 cating, Dr. Buckland observes, " the habit of these fishes to have been 

 to feed on decayed sea- weed, and soft animal substances at the bottom 

 of the water." 



In the large enamel-scaled fishes of the Lias formation belonging 

 to the genera Dapedius and Tetragonolepis, the teeth are stronger and 

 better developed, especially the exterior ones. In the Tetragonolepis, 

 the summit of the crown is simply pointed, but in the Dapedius it is 

 notched or bifurcate ; and this modification is not due to usage or 

 compression, for the teeth of all the rows and in both jaws exhibit the 

 same character, which is also well marked in the successional teeth 

 that have not come into place. In Dapedius Orbis, the teeth of both 

 jaws are strongly dilated and compressed from before backwards, 

 at their summits, and resemble a chisel with a notched cutting 

 edge.(l) 



In the extinct genus Lepidotus, the mouth was small and 

 the jaws short and rounded. The intermaxillary bones form only 

 the anterior part of the upper margin of the mouth, the maxillaries 

 completing the posterior part of that border. The margins of both 

 these bones, according to M. Agassiz, are beset with small teeth ; the 

 outer row presenting the form of circular obtuse cones ; and within 

 these are many rows of smaller sessile hemispherical teeth, more or 



(1) M. Agassiz assigns pterygoid, as well as palatine and intermaxillary teeth to the genus 

 Dapedius, t ii, p. 187. 



