148 MEMOIRS OP THE UNIVERSITY OF CALIFORNIA. 



i 



MlXOSAURIDAE OP UNCERTAIN POSITION. 

 CYMBOSPONDYLUS (?) NORDENSKIOLDII (Hulke). 



is norden-skioldii Hulke, Beihang. K. Svenska Vet. A. Handlinyar. Bd. 1, 



no. 1. 

 MLrosaurus nordenskioldii (Dames), Sitzb. der Acad. der Wiss., Berlin, 1895, p. 1047. 



To this species Hulke referred a number of vertebrae and ribs obtained by 

 A. E. Nordenskiold in the Triassie of Saurie Hook, Spitsbergen. 



The specimens referred to this species represent a smaller form than C.(?) 

 polaris. The vertebrae present represent the thoracic and caudal regions. The 

 dorsal vertebrae (2r/) described by Hulke are subcircular, slightly angular, and 

 approaching a hexagonal form in anteroposterior profile, the greatest width or 

 transverse diameter nearly equaling the height. The height is about 1.65 in. 

 The anteroposterior diameter is .35 in. They show anterior and posterior artic- 

 ular surfaces which are unequally hollow. On one centrum the diapophysial 

 articular surface is apparently confluent with the neurapophysial articular 

 surface. The interval between the diapophysis and parapophysis exactly cor- 

 responded to the interval between the tuberculum and capitulurn of a rib near 

 by. As it is described, this vertebra might represent a posterior cervical or an 

 anterior dorsal of either a shastasaurine or an ichthyosaurine form. 



The caudal vertebrae referred to this species were recognized by Hulke as 

 differing markedly from the caudals of the typical Ichthyosaurus, but their 

 reference to an ichthyosaurian seemed unavoidable owing to their association 

 with unmistakable tabular, polygonal ossicles plainly belonging to an ichthyo- 

 saurian paddle. The caudal centra were characterized by having a vertical 

 diameter relatively long as compared with the transverse diameter. The artic- 

 ular faces of the caudals were characterized by a small but deep pit immedi- 

 ately below the middle. 



The dimensions of a caudal (series 2, d Hulke) were : anteroposterior diam- 

 eter, .3 in. ; vertical diameter, about 1 in. ; horizontal transverse diameter, .6 in. 



The caudal centra of this species in their general form resemble the centra 

 of the distal third of the caudal region in Cymbospondylus (see pi. 9, figs. 8 

 .and 8&), and of other shastasaurine forms, and do not differ greatly from those 

 of Mixosaurus. (See fig. 124, p. 96.) 



Two fragments forming part of the snout of a reptile were found by Hulke 

 in the Nordenskiold collection from Spitzbergen, and were considered as prob- 

 ably belonging in the genus Ichthyosaurus. The anterior teeth were smaller 

 than the posterior ones, and were set in an open continuous groove. The pos- 

 terior teeth were found to occupy separate sockets, the dentary groove being- 

 interrupted in this region by transverse partitions between the teeth. All of 



