258 W. Davies — On SaurocepJialus. 



" The finest specimen of this species hitherto discovered belongs 

 to Mr. Bowerbank ; it shows the extremities of the two rami of the 

 lower jaw ; the dentary bones thicken out as they converge to the 

 symphysis to give space for the implantation of six large lanciform 

 teeth, which project forwards nearly in a horizontal direction ; the 

 dentary bone immediately behind the symphysis is armed on its 

 inner edge with strong laniary teeth ; the two hinder ones being ou 

 either side considerably larger than those that precede them ; the 

 specimen is broken off a short distance from the commencement of 

 the outer row, the anterior teeth of which are small." ^ 



We have here many essential points in which the two specimens 

 agree, the main points of difference being the anterior row of small 

 lancet-shaped teeth upon the outer border of the dentary bone in the 

 American species, but which are not present in the British specimen, 

 which has the anterior teeth of the dentary bone in one continuous 

 series, with smaller teeth in advance of the larger ; the small teeth 

 of the outer border commence about half an inch behind the last 

 laniary tooth of the inner border. 



To the above description may be added the satisfactory evidence of 

 the mode of succession of the teeth. This is shown by the bases of 

 the first laniaries, as also those of the upper and horizontal teeth of 

 the symphysis on either ramus of the mandible having been absorbed 

 to make room for the successional teeth, the apices of which are 

 23 resent in each alveolus excepting that of the right laniary, which 

 has been lost ; they abut against the absorbed portions of the fangs, 

 and are thus developed, as in Mosasaurus and other Lacertians, ou 

 the outside, and not within the pulp cavity of the mature tooth. 



I had written the foregoing remarks, when my friend Mr. E. T. 

 Newton, F.G.S., of the Jermyn Street Museum, to whom I had shown 

 a portion of the manuscript, very kindly called my attention to a paper 

 "On the genus Erisichthe^' published in 1877, in the sixth Bulletin 

 of the U.S. Geological and Geographical Survey, a copy of which he 

 had received from Prof. Cope ; and I publish them as an instance of 

 not uncommon occurrence, of an independent conclusion derived from 

 an actual study of special objects, in some degree confirming what 

 had already been accomplished by other investigators. 



In this paper Prof Cope has identified and described three species 

 of ErisicJithe from Kansas, and concludes with the following para- 

 graph: "A fourth species has been found in England, and figured by 

 Dixon in the ' Geology of Sussex.' The portions represented in this 

 work are the mandibles, which resemble those of E. niticla, and which 

 were supposed at that time to belong to a species of Saurocephalvs. 

 A muzzle, perhaps of the same species, was regarded as a Sword-fish, 

 which was called Xiphias Dixonii by Agassiz." This is an error; the 

 name, as we have seen, was given by Leidy. He continues, •' It 

 should be now termed Erisichthe Dixoni." 



With regard to the genus, he remarks that "ErisicJithe nitida, Cope, 

 was originally represented by a few portions of the skull ; among 

 other pieces, the premaxillary and dentary bones being present. The 

 1 Dixon, Geol. Suss. pp. 374, 375. 



