Ma?ichester Memoirs, Vol. liv. {igog), No. 4. 13 



Type species " Plesiosauriis " homalospoudyhis, Owen. 

 Zone of D. commune, Whitby, and H. bifrons, Welling- 

 borough. 



Characters those of the genus, of which it is the only 

 known species. 



A set of six or seven cervical vertebrae of this type in 

 the Jermyn Street Museum is said to have been obtained 

 from the Lower Lias of Gloucestershire. 



The New Genus and Species, Sthenarosaurns 

 Dawkinsi. 



The material on which this species is founded is in 

 the Manchester Museum. It was collected by W. H. 

 Sutcliffe, Esq., from the D. commune zone of the Upper 

 Lias of Saltwick, some 10 feet above, and lOO yards away 

 from, the specimen of Microcleidus described above. 



The skeleton is scattered, although the girdles are 

 still nearly naturally arranged ; the bones present are 18 

 cervical vertebrae, 1 1 dorsal vertebrae, 4 caudal vertebrae, 

 complete pectoral and pelvic girdles, 2 humeri and 2 

 femora, both tibiae and fibulae and many tarsals and ribs. 



The cervicals vary much in size, the smallest has a 

 centrum measuring 3'5 cm. in height, 3'5 in length, and 

 4"5 in width ; the corresponding dimensions of the largest 

 are 6 cm., 6 cm., and 7'5 cm. ; it is thus nearly twice the 

 size of the smallest. 



The vertebrae preserve a very uniform character 

 throughout the neck. The anterior end of the centrum is 

 rather deeply cupped, the posterior end, although not 

 nearly flat, being much less so. The ends of the centra 

 are somewhat heart-shaped. Viewed from below the 

 centrum shows a very marked haemal ridge, on each side 

 of which is a deep depression in which and close to the 

 median line lie the usual two foramina for nerves and 



