254 



University of California. 



LVOL. 3. 



rather prominent apophyses. The centrum is hexagonal in 

 cross-section, the inferior surface and the lateral areas above and 

 below the diapophyses being flat or slightly concave. 



The ribs are very imperfectly preserved and only one speci- 

 men was found in which the form of the head and shaft can be 

 seen distinctly. The single head is twisted backward and both 

 sides of the shaft are grooved, the posterior more deeply than the 

 anterior. The form of this rib is similar to that in the dorsal 

 region of Shastasaurus perrini. A great many of the abdominal 

 ribs are present in their original positions. They are in five 

 linear series like those of Ichthyosaurus. 



Anterior arch. — Excepting the clavicles and the inter-clavicle, 

 which had slipped forward a short distance, the bones of the 

 pectoral girdle were all in their natural positions, with the limbs 

 in place on each side. The coracoids (PI. 21, fig. 2) are very 

 much expanded antero-posteriorly. Their diameter measured in 

 this direction is twice the length of that taken transversely. Their 

 form is roughly elliptical. The anterior and posterior ends are 

 gently-rounded and there is no trace of an anterior or posterior 

 emargination. There is no pedunculation of the portion artic- 

 ulating with the humerus and scapula as in Shastasaurus and 

 Mixosaurus, though the proximal portion is considerably thick- 

 ened. The portion next the median line is considerably thickened 

 by a high ridge running obliquely forward. The scapulce (PI. 21, 

 fig. 2) are short and broad, having the general form seen in 

 Shastasaurus. The articular surface is curved so as to form two 

 fairly distinct facets for the coracoid and humerus. The anterior 

 hook is shorter and the notch below it not so well marked as in 

 Shastasaurus osmonti or alexandrce. As the posterior angle of 

 the upper margin is very thin, it probably did not extend far 

 beyond the limits given in the figure and was therefore shorter 

 than in S. osmonti. 



The clavicles (PI. 21, fig. 1) are represented by two heavy, 

 broad bars meeting, or possibly overlapping, on the median line 

 in front of the coracoids. The ends next the scapulae are broken 

 away so that the total length of these elements can not be 

 determined. The ends next the median line are considerably 

 broadened and are concave on the posterior side. As far as can 



