88 



University of California. 



[Vol. 3 



type specimens were available for comparison. Of the species 

 mentioned, heciori, polaris, and nordenskjoldi do not appear to 

 have yet been figured. The illustrations of carinatus and rhceficus 

 are very imperfect. An outline drawing giving the limb structure 

 of cornalianus was furnished by Baur, and Frass has published 

 good figures of scattered vertebra? of atavus, together with jaw 

 fragments and a doubtful humerus. 



The figure of cornalianus shows the structure of its anterior 

 limb to be more primitive than that of either the anterior or the 

 posterior limb of Shastasaurus , but gives us no hint as to the 

 most important characters of that genus. The figures of the 

 vertebra* of atavus minor, given by Frass, show separate dia- 

 pophyses and parapophyses low down ou the centra, indicating 

 that it is entirely different from Shastasaurus. The zygapophyses 

 of the upper arches are also more nearly vertical and do not come 

 so near to being in the same plane. It is clear that no very close 

 relationship can be found with these two species or the genus 

 which they represent. 



In his description of rhmticus, Sauvage states that the dia- 

 pophysis and parapophysis on one dorsal vertebra are united, 

 and one might almost suppose that there existed here the modi- 

 fication found in the Calif ornian species. However, in the 

 description of another dorsal, he states that they touch in form- 

 ing a figure eight, and in his illustration of this specimen, they 

 are seen to be close together but quite distinct . The diapophysis 

 appears also to be separate from the neurapophysial surface of 

 the centrum so that the similarity to Shastasaurus is not so great 

 as might appear from the description. On the other hand, notice 

 should be taken of the very large di- and parapophyses, such as 

 are not, to the writer's knowledge, found in Ichthyosaurus. 



Concerning carinatus, little can be said excepting that both 

 diapophyses and parapophyses are mentioned as being on a 

 centrum which is evidently a dorsal. 



Of the nnfigured forms very little can be determined. Accord- 

 ing to the descriptions, Hulke's polaris agrees very well with 

 the posterior dorsals of Shastasaurus, and later examination may 

 show that it belongs to that genus. 



It is hardly to be doubted that future exploration and investi- 



