. 161 



its locality and horizon. Numerous North American species resemble it in 

 the forms of the crowns of the teeth, and it is probable, though not certain, 

 that they agree in other respects also. Several names have been proposed 

 for our species, the earliest of which is Macrosaurus, Owen. This name 

 applies to species with compressed dorsal vertebrae, as L. Icevis and L. mitch- 

 illii, both from the New Jersey greensand. For the species with depressed 

 dorsal vertebras, as L. validus from New Jersey, L. perlatus from Alabama, 

 and L. proriger from Kansas, the name Nectoportheus was proposed, and 

 briefly characterized (Extinct Batfachian Eeptilia of North America, 1870, p. 

 208). Professor Marsh subsequently gave the Kansas species the name 

 of Rhinosaurus, which name being preoccupied more than once, I changed it 

 to Rhamphosaurus. 1 This name will remain for species of the type of L. 

 proriger, if they be found to represent a genus distinct from Nectoportheus or 

 Liodon, of which there is as yet no evidence. 



LlODON PKORIGER, Cope. 



The original description of tins large Mosasauroid was based on material 

 in the Museum of Comparative Zoology, Cambridge, Mass., brought by Prof. 

 Louis Agassiz from the Cretaceous beds in the neighborhood of Monument, 

 Kans., and near the line of the Kansas Pacific Railroad. It consists of the 

 greater part of the muzzle from the orbits, with the right dentary and left 

 pterygoid bones nearly complete ; one cervical vertebra (with hypapophysis) ; 

 one dorsal; one caudal with diapophysis; and ten caudals without diapophysis. 



The charactei-s presented by the vertebral column indicate an exceedingly 

 elongate reptile ; the transverse diameter of one of the distal caudal vertebras 

 is less than one-fifth that of a proximal with short diapophysis ; while four 

 consecutive ones of the former show but little variation in dimensions. This 

 diminution amounts to two-sevenths of a transverse diameter of the larger 

 form. With this ratio as a basis, fifty-three two-thirds vertebrae would form 

 a complete series from caudals one-half the diameter of the last of the four 

 to the proximal caudal above mentioned. There have been, no doubt, several 

 caudals in advance of the latter, as the diapophyses are small. From the 

 slow rate of diminution of the columns of other species examined, it may be 



1 This Dame was applied by Pitzinger to two species of lizai.ds which had already received generic 

 names, and hence became at onco a synonym. Further he did not characterize it. For these reasons, tho 

 name was not preoccupied at the time I employed it as abovo ; hence there is no necessity for Professor 

 Marsh's subsequent name Tylosanrus, given on the supposition of preoccupation. 



21 c 



