MERRIAM THE THALATTOSAURIA 35 



Arches. 



Coracoid (No. 9085), antero-posterior diameter 65 



transverse diameter of median portion 33 



Scapula " greatest length 55 



Ischimn (?) " " " 72 



'• " width 26.5 



Pubis(?) (No.9044), " lengtli 106 



" width 47 



Linihs. 



Humerus (No. 9084), greatest length 75 



" '• " width, proximal end 39 



" " " " median portion 21 



" " " " distal end 52 



thickness of distal end '. 18.5 



Radius " " length V,40 



" " " width, distal end a29 



" " " " median portion 15.5 



Ulna (No. 9085), greatest length 40 



" " width, median portion 25 



Thalattosaurus shastensis, n. sp. 



Plate III; Plate IV, Figs, lio-e; Plate VII, Fios. 4, 7; Plate VIII, Figs. 3, 7, 8. 

 Type specimen No. 9120 Univ. Calif. Palae. Coll. 



Conipai'ed with T. akxandrae tlie individuals are consideral)ly smaller: the 

 scapula, liunierus and ulna more slender; the nasal openings shorter and that 

 portion of nasal bones behind the openings longer and broader; the neural s})ines 

 of the dorsal vertebrae are possibly shorter. The conical teeth associated with 

 the type specimen show more numerous and more closely set longitudinal striae 

 than are seen in tlie jaw teeth of T. alexandrae. There is of course a possil)ility 

 that these teeth belong to the pterygoids and not to the jaws. 



This species appears to be very near the type form of the genus and may be 

 shown later to be identical with it, possibly representing young individuals. 

 There are, however, several specimens in the collection which seem to have the 

 same characters and to be slightly removed from T. alexandrae. 



This form is not uncommon, and ranges from the Trachyceras horizon almost 

 if not quite to the top of the Hosselkus Limestone. It is known only from the 

 Triassic of Sha.sta County. 



la, approximate. 



