101 



its locality and horizon. Nuinc rons Norlli American spocies rescmhle it, in 

 the I'ornis of tlio 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 vertebra?, as L. Icevis and L. mi.tch- 

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

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

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

 briefly characterized (Extinct Batrachiaii Reptilia of North America, 1870, p. 

 208). Professor ]\larsh subsequently gave the Kansas species the name 

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

 to Rhampliosaurus} This name will remain for species of the type of L. 

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

 Liodon, of which there is as yet no evidence. 



LlODON PROKIGER, Cope. 



Tiie original description of this 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 characters presented by the vertebral column indicate an exceedingly 

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

 is less than one-fifth that of a jvoximal 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 vertebra? 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 



' This name was applied by Fitzinger to two spucies of lizards which had already received generic 

 nonies, and hence becatiio at once a synonym. Fnrtlicr he did not characterize it. For these reasons, tlio 

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

 Marsh's subscqiieut name Tylusanrus, given on the snpposition of preoccupation. 



21 c 



