VERTEBRATE PALEONTOLOGY IN 1909 669 



to the existing Sphenodon on the one hand and to the extinct 

 Homceosaurus on the other. 



In addition to his work on the steneosaurs Dr. Andrews has 

 devoted his attention during the year to the plesiosaurians of 

 the Peterborough Oxford Clay, with the result that he has found 

 himself in a position to describe, in the Annals and Magazine of 

 Natural History, ser. 8, vol. iv. pp. 418, 429, three new generic 

 types. The first of these, Tricleidus seeleyi, is a small elasmo- 

 saurian plesiosaur allied to Cryptocleidus but distinguished by 

 the shortness and width of the skull, the presence of twenty 

 pairs of teeth, the existence of basisphenoid processes on the 

 pterygoids, the broad and abruptly truncated parasphenoid and 

 the possibility of the existence of two distinct elements in the 

 quadrate region. There are twenty-six vertebrae in the neck. 

 The second genus, Picrocleidus, established for the Murcenosaurus 

 veloclis of Seeley, is a longer-necked small plesiosaur, having no 

 less than thirty-nine cervical vertebrae, all characterised by the 

 shortness of their centra, of which the terminal faces are nearly 

 flat and wider than high. The interclavicle, unlike that of 

 Tricleidus, is reduced to a small triangle of bone, while the 

 clavicles, if present at all, form mere filmy splints. 



Of still greater interest is a blunt-nosed pliosaur described 

 as Simolestes vorax and distinguished by the shortness and width 

 of the skull, in which the snout lacks the elongation charac- 

 teristic of both Pliosaurus and Peloneustes. The two halves of 

 the lower jaw meet in a short symphysis, of which the inferior 

 surface makes a marked angle with the lower border of the 

 ramus itself. Simosaurus may be related to the imperfectly 

 known Thaumatosaurus of the Lower Oolite of Wurtemberg ; the 

 author suggesting that the Liassic forms referred by the present 

 writer to the latter are generically distinct. 



Plesiosaurians from Russia form the subject of a paper by 

 Prof. A. Riabinia, published in Mem. Comm. Geol., St. Petersburg, 

 livr. 43, in which the Engish Peloneustes philarchus is identi- 

 fied from Jurassic deposits and Cimolioscarus bernhardi from 

 other beds of Cretaceous age. From presumably Kimeridjian 

 strata at Simbirsk, on the Volga, Mr. N. Bogoluboro, in Ann. 

 Geol. et Min. de la Russie, vol. xii., describes a new plesiosaur 

 under the name of Cryptocleidus simbirskensis. 



The same author, in the paper cited, likewise names a new 

 ichthyosaur (Ichthyosaurus steleodon), from the Neocomian strata 



