128 



MEMOIRS OF THE UNIVERSITY OF CALIFORNIA. 



Limbs with three digits and a rudimentary fourth. Epipodial segments elon- 

 gated and enclosing a wide space. Radius with median constriction, ulna 

 notched only on the median border. Proximal row of mesopodial region in- 

 cluding only three elements. Carpals and tarsals in linear series. Phalanges 

 generally notched on one or both sides. Ischiurn and pubis plate-like ; pubis 

 very broad, and with obturator foramen. Ilium slender and elongated. 



The type specimen, no. 8100, was obtained in the upper portion of the Tra- 

 chyceras Beds at Bear Cove, on the east side of Brock Mountain, between Pit 

 River and Squaw Creek, Shasta County, California. Other specimens evi- 

 dently to be referred to this genus are known from the Trachyceras Beds. 



Toretocnennis is distinguished from all of the other American Triassic ich- 

 thyosaurs by the double rib articulation of the middle dorsal region. (See 

 fig. 59, p. 49.) In the characters of the limbs it has much in common with the 

 genus Merriamia, excepting that the posterior limbs are relatively large. The 

 pelvis is more primitive than that of any other Upper Triassic ichthyosaurian. 

 (See fig. 69, p. 55.) It differs from the posterior arches of other Triassic 

 forms, excepting -Cymbospondylus, in the enclosing of the obturator foramen. 

 The ilium seems to be more slender than in any other known form. 



TORETOCNEMUS CALIFORNICUS Merriam. 

 Toretocnemus californicus Merriam, Univ. Calif. Publ. Geol., vol. 3, p. 251, pi. 24. 



The type specimen, no. 8100, Univ. Calif. Col. Vert. Palae., is the only de- 

 termined material which has been completely exposed for study. A number 

 of other small specimens from the same beds show similar 

 characters. The type specimen was found embedded in a 

 thin slab of shaly limestone which had been weathered in 

 such a manner as to destroy a considerable part of the skele- 

 ton. The remaining fragments are not far removed from 

 their natural positions. The parts present represent small 

 fragments of the head, a vertebral series extending from the 

 middle dorsal region to the middle of the tail, the pelvis nearly 

 complete, the proximal half of both posterior limbs, a part 

 of an anterior limb, and numerous ribs. 



This was the first American Triassic ichthyosaur in which 

 the constricted phalangeal elements (fig. 139) were discov- 

 ered. In the character of its limbs and pelvis this is the most 

 primitive American Upper Triassic form. Whether the bi- 

 Fi Toretoc- ms ip^al rib articulation of the middle dorsal region indicates 



caiifomicus Merriam. primitive characters may perhaps be open to doubt. It is 

 oral size, *R, rWuus. nevertheless most nearly paralleled by the structure of some 



