69 



its deep pits in longitudinal lines. The angle of the mandible is depressed. 

 The cotylus of articulation is partially concealed on the 6uter side by the ele- 

 vation of the surangular, whose upper border is parallel with the inferior 

 margin of the ramus for two inches to where it is broken off. The outer face 

 of this region is marked by irregular coarse ridges, more or less inosculating, 

 separated by deep pits. The lower posterior half of the angular bone is 

 smooth. 



A posterior dorsal or lumbar vertebra has a depressed cordate articular 

 cup. The zygapophyses are large and widely spread, and strengthened by 

 obtuse ridges running from the base of the neural spine to the posterior 

 margin of the anterior, and the posterior outer angle of the posterior. One 

 pit at basis of neural spine in front; two before. Ball prominent: sides of 



centrum concave. 



Measurements. 



M. 



Lergth of a fragment of the ramus 0. 100 



Width iu flout 0.034 



Depth behind 0.032 



Length of eight alveoli 0. 00!) 



Diameter of the largest alveolus- 0. 012 



Diameter of the smallest 0. 007 



Width of the base of the angle of the ramus 0. 04S 



Depth at surangular 0.034 



Length of the centrum of the vertebra 0. 045 



Width of the articular cup 0. 031 



Vertical diameter of the articular cup 0. 025 



Vertical diameter of the neural arch 0. 011 



Expanse of the anterior zygapophyses 0. 05C 



The specimen is adult, and indicates an animal about the size of the alli- 

 gator of the Southern States. Its reference to the present genus is provisional 

 only. 



SAURGPTERYGIA. 



As compared with the European and New Zealand Cretaceous beds, 

 those of our country have yielded but few remains of reptiles of this order. 

 Four only arcembraced in the present, work, three of which are from No. 3, 

 and one from No. 6. 



The structure of the scapular arch in Pohjcotylus is yet unknown ; in 

 Elasmosaurus, it is quite distinct from that of Plesiosaurus, so much so as to 

 have induced me to regard it as type of a distinct family, the Elasmosauridce, 

 characterized by the absence of distinct mesosternal bone. Professor Seeley 

 has since more fully defined this group, and has discovered several species of 



