1916] Wiman: Marine Triassic Reptile Fauna of Spitzbergen 69 



the figures of Pessosaurus polaris Hulke and Shastasaurus osmonti 

 Merriam proves that quite another type is before us. The coraeoid 

 undeniably shows a certain likeness to the same bone in Shastasaurus, 

 but it is more elongated longitudinally, which, however, is of little 

 importance. This type of humerus differs widely from all the Amer- 

 ican species and recurs only in Pessopteryx, the species of which, one 

 and all, possess this thick, round type. Also radius and ulna have an 

 appearance diverging very much from all other forms, caused by their 

 belonging to a species with short, broad fins, within which the dis- 

 placement of the bones has proceeded farther than with any other 

 Triassic ichthyosaurian. For though the, for all such typical remain- 

 ing portion of the forearm, elongation still is marked by the round not 

 cartilage-filled hole between the radius and the ulna, the intermedium 

 has pressed in just as far between the forearm bones as, for instance, 

 in the Jurassic Ichthyosaurus communis Conyb. The fore limb of 

 Pessosaurus thus shows arrangement and form of the bones quite 

 different from the corresponding characters in Shastasaurus. 



PESSOPTERYX AND OMPHALOSAURUS 



The material from the Lower Saurian horizon of Spitzbergen is 

 very difficult to handle, as it consists of mere loose bones and bone 

 fragments which lie scattered on the float soil. Most of the bones are 

 present in a very great number of specimens, and I still consider it 

 probable that the majority belong to an ichthyosaurian which I have 

 called Pessopteryx nisseri. In addition, some smaller species chiefly of 

 the same time must be present. 



To Pessopteryx nisseri I also referred, by way of proposal, and 

 with much hesitation, a large number of jaw fragments with queer, 

 button-like teeth in several rows. When I referred these teeth to an 

 ichthyosaurian I imagined a change of diet something like the one 

 that has now really been verified in Phalarodon and Globidens. That 

 the teeth were set in several rows I imagined to be due to the fact that, 

 for the greater part at least, they consisted of reserve teeth, not yet 

 used, which in that case ought to be arranged much the same as with 

 the crocodiles, although, as far as I have yet been able to ascertain, 

 they lie wholly embedded in the bone substance. Resorption of bone 

 substance is of course nothing unusual in connection with displace- 

 ment of teeth and horny cases, and also the embryological origin of 

 similar teeth ought to be histologically possible. 



