MERKIA.M: THIASSIC K'UTI! YOSAI'IMA. 1l'!) 



of the earliest known European forms. The elongated vertebral centra are 

 evidently of a more primitive form than the shorter centra of the shastasaur- 

 ian type. 



MKUUIA.MI \ IJoulengcr. 



L<-l>locli<in<x .M(>rriani. Univ. Calif. I'nhl. (ieol., vol. 3, p. 251. .May, ]!)():{. Preoccupied 

 by 



Mcn-iatnia- Boulen^cr. 1'roc. Zoo]. Sue. Loncl., vol. i. p. 42."). Auir. 2. 1!)(I4. 



Caudal vertebrae with elongated centra. Dorsal ribs single-headed. Cora- 

 coid elliptical, without pedunculation or emargination. Scapula with distal 

 expansion and short anterior hook. Posterior limbs much smaller than ante- 

 rior. Limbs with three digits and a much reduced rudiment of a fourth. 

 Epipodial elements elongated and separated by a wide gap. Proximal row of 

 mesopodial region with three elements, and intermedium supporting but a 

 single element distally. Phalanges generally notched on one or both lateral 

 margins. Angular element of mandible relatively small. Dentition undiffer- 

 entiated. tooth crowns conical. 



The genus is distinguished from Torctocnemus by the relatively small pos- 

 terior limbs, and the single-headed rib articulation of the dorsal region. It 

 differs from Delphinosaurus greatly in the form of the known elements of the 

 limbs and of the pectoral arch. Shastasaurus represents a type of speciali- 

 zation somewhat similar to that of Delphinosaurus but much more extreme. 

 Mi-cosaurus differs very considerably in the whole structure of the limbs, 

 arches, and dentition. 



This genus is represented by a single species occurring in the Trachyceras 

 Beds of the Upper Triassic limestones of Shasta County, California. 



MERRIAMIA ZITTELI (Merriain). 



Leptocheirtu zittcli Merriain, Univ. Calif. Publ. Geol., vol. 3, p. 253, pis. 21, 22. and '2'.]. 

 M( rriamia zitteli (Boulenger), Proc. Zool. Soc. Lond., vol. i, p. 425. Aug. 2, 1904. 



The type specimen, no. 8099, Univ. Calif. Col. Vert. Palae., was found in 

 the Trachyceras Beds of the Hosselkus Limestone at Smith's Cove, between 

 Squaw Creek and Pit River, Shasta County, California. It includes about 

 one-half of the skull, the pectoral arch and limb, a large part of a pelvic limb, 

 with a number of vertebrae, ribs, and abdominal ribs. In this form the tri- 

 dactyl type of limb is better expressed than in any of the other Triassic forms 

 known (figs. 140 and 141). A somewhat similar form of limb is seen in some 

 of the longipinnate forms of Ichthyosaurus, as /. acutirostris Owen, I. plat i/- 

 oiloti Conybeare, and /. tcinn'roxtri* Conybeare. 



With the pectoral arch of the type specimen of this species the clavicles 

 were present in front of the coracoids. They are represented by two broad 



