Geological Papers. m 



MY EXPEDITION TO THE KANSAS CHALK FOR 1907. 



Hy Chaiu.es II. Sxeunbeug, Lavvronce. 



I T still remains my privilege to tell this Academy of another 

 ^ successful expedition in the Chalk of Kansas during the 

 past season. My oldest son, who has been my chief assistant 

 since he was twelve years old, feeling that he was perfectly 

 capable of carrying on my work in the field without my pres- 

 ence, insisted on my remaining at home in my laboratory. He 

 promised to keep me busy by sending in new material. 



I am delighted to tell you that he did all he promised to, and 

 I was well satisfied with the results. I was indeed kept busy 

 opening boxes and preparing the tons of fossils he sent to me, 

 and it was almost as great a pleasure as to find it myself, with- 

 out the discomforts attending the actual discovery in the field, 

 to open up to the light a finely preserved specimen collected by 

 the second generation of fossil hunters. He sent me the best 

 specimen of the great ram-nosed Tylosamnts dyspelor I have 

 ever discovered. The entire column, except a few caudal verte- 

 brae, are present, many continuous. And, strange to tell, for 

 the first time the minute last caudal vertebrse are present, the 

 last six measuring a fraction over an inch in length, and the 

 terminal one a mere nodule of bone, less than three-tenths of 

 an inch in diameter. There are about 126 vertebrse, instead of 

 116, according to the skeleton described by Doctor Williston. 

 So the number must vary, or the last minute ones had been 

 lost in the University specimen. Further, the caudal vertebrse 

 decreased in all their proportions regularly; each one is a 

 millimeter smaller than the preceding one. Consequently, as 

 I believe, the mounted and restored Bourne specimen, in the 

 American Museum, with a short, crooked tail, is abnormal, and 

 not natural, as Doctor Osborn was led to believe. I have an- 

 other specimen I will mention later, of the same size, in which 

 the tail turns up in the same way that their specimen turns 

 down. Tylosawus has a long, flexible, eel-like tail. 



Another fine specimen sent from the field was a complete 

 skull, with mandibles, of a new species of the Cretaceous sea- 

 tortoise Toxochelys. This I believe belongs to the new species 

 of which I sent to Yale a couple of years ago a nearly complete 

 carapace and plastron, described by Doctor Weiland as Toxo- 



