W. C. Knight — Notes on the Genus Baptanodon. Y9 



the material in hand and wrote Dr. Beecher concerning the 

 material at Yale University, and he informed me that the ones 

 examined by him in the Yale collection had but two facets, 

 and that the humerii had three but one was very small. The 

 fact that Baptanodon so far as known has but two elements 

 articulating with the femora is worthy of special consideration. 

 Yertebral Column. — The specimen S in the Wyoming col- 

 lection contains 41 precaudal vertebrae. These are consecutive 

 and represent the series from the head backwards. The atlas 

 and axis are so completely fused that there is not the slightest 

 trace of their union. Anteriorly the first vertebra (atlas and 

 axis) is only slightly excavated ; but upon this elongated verte- 

 bra there are two normal or almost normal processes. The 

 first vertebra (atlas and axis) is 41™^ in length, and the second 

 is only 31°'"' long. There is no intercentra between these (the 

 second and third) vertebrae. It is also questionable whether there 

 is any between the atlas and axis and the axis and the basioci- 

 pital. If they are present they are so perfectly anchylosed to 

 the centra as to make it impossible to distinguish them. I 

 have only examined a single specimen, and while I think it 

 possible that all of the intercentra have disappeared, it will be 

 desirable to make further examinations before this point can 

 be passed upon. In specimen S the vertebra gradually increase 

 in length and width from the atlas and axis to ]No. 19; the 

 third vertebra being 31™"" long and 80°^°" wide and the nine- 

 teenth 41™'' long and 90'""' wide. These are separated by 

 intercentra measuring from 10 to 15°"". From No. 19 back- 

 wards to the end of the series the vertebrae decrease slightly 

 in length and width. In specimen T in the same collection 

 there are 46 consecutive caudal vertebrae. These are of the 

 usual ichthyosaurian type, and represent an animal that had 

 an extremely long and slender tail. The reduction in the size 

 of the vertebrae occurs very near the body and within a dis- 

 tance of a few inches the vertebrae decrease in diameter over 

 one-half. The vertebrae in the area of reduction have reduced 

 margins, in fact in two of them the articulations nearly meet 

 upon the side of the centrum. This signifies that the tail was 

 extremely flexible near the body, which would make it of 

 great value in swimming, and without question this animal 

 could lash its sides with its tail. I have not noted anything of 

 this kind in the genus Ichthyosaurus. Although caudal verte- 

 brae from at least a half dozen different animals have been 

 examined, no trace of chevrons has been observed, and the 

 vertebrae lack chevron facets. 



Pectoral Girdle. — The coracoids are broadly elliptical bones, 

 anteriorly deeply and broadly notched ; posteriorly circular. 

 They thicken rapidly from the center to the interior margin 



