December 5, 1902.] 



SCIENCE. 



913 



from Mrs. J. M. Arms, who is in charge of 

 nature study in the schools of Boston, Mass. : 

 Nature study is simply the study of na- 

 ture, not the study of books. It is a course 

 of nature lessons especially adapted for ele- 

 mentary schools. Minerals, rocks, plants and 

 animals are the necessary materials for such 

 lessons. The method of study may be ex- 

 pressed in three words, observation, compari- 

 son, inference. The child must be made to 

 see the object he looks at, and to this end he 

 tries to draw it and to describe it in writing. 

 Comparative work is mental training, which, 

 combined with the observational training 

 already spoken of, gives a certain degree of 

 mental power. This power gained in the 

 early years increases with continued effort. 

 Fortunately, this work is recognized as one of 

 the potent agencies in producing efficient men 

 and women equipped for a life work that shall 

 make for the betterment and enlightenment of 

 humanity. 



SHORTER ARTICLES. 



DISCOVEHY OF TEETH IN BAPTANODON, AN ICH- 



THYOSAURIAN FROM THE JURASSIC OF 



WYOMING. 



Among the vertebrate fossils collected by 

 Mr. 0. A. Peterson during the season of 1900 

 on Sheep Creek, Albany County, Wyo., there 

 was obtained from the lower beds of the Ju- 

 rassic a very complete skull of an Ichthyo- 

 saurian reptile (Baptanodon discus f) together 

 with a few vertebrae and ribs. 



Through the courtesy of Mr. J. B. Hatcher, 

 curator of the Department of Vertebrate 

 Paleontology of the Carnegie Museum, this 

 material has been placed at the disposal of 

 the writer for study and description. 



Heretofore the American Jurassic Ichthyo- 

 saurians were supposed to be edentulous, but 

 while preparing this specimen (No. 603) for 

 study the remarkable discovery was made that 

 the jaws bore teeth, two of which were found 

 between the jaws near the end of the snout. 

 One tooth was apparently in position in the 

 upper jaw, while the other lay imbedded in 

 the matrix between the jaws and entirely de- 

 tached from them. The teeth are small, 

 conical, and covered with longitudinal strise. 



In general form and surface markings they 

 resemble very closely the teeth of the Liassic 

 Ichthyosaurs of England and Europe. The 

 teeth were undoubtedly loosely fixed in the 

 jaws and have been lost in all previously dis- 

 covered specimens. In the present skull a 

 few of them have fortunately been retained, 

 and we have here the first evidence of their 

 presence in Baptanodon, which may be re- 

 garded as the American representative of the 

 Ichthyosaurian reptiles. 



When the skull is entirely freed from the 

 matrix and the jaws separated from one an- 

 other, more teeth will doubtless be exposed. 



From the above evidence it would appear 

 that the generic terms Baptanodon (Saurano- 

 don) of Marsh * are misnomers. 



The reduction in size and number of the 

 teeth in the Jurassic Ichthyosaurians is par- 

 alleled in some of the recent Cetacea. Most 

 if not all of the early (Eaeene and Miocene) 

 cetaceans were well provided with functional 

 teeth, while in many modern forms these 

 either have been entirely lost or have become 

 rudimentary, in some instances appearing 

 only in the embryonic or young stage of the 

 individual. Just so the early Ichthyosaurs 

 were provided with an abundance of teeth, 

 but in later forms the number and size of the 

 teeth were reduced, until in Baptanodon a 

 form was developed which, while still possess- 

 ing teeth, was practically edentulous. 



Ichthyosaurus longirostris as described by 

 Owen,t was in this respect intermediate be- 

 tween Ichthyosaurus longifrons from the Lias 

 of England and Europe, and Baptanodon dis- 

 cus of the American Jurassic. 



The presence of teeth, though undoubtedly 

 reduced in number and in size in American 

 Ichthyosaurians, may perhaps be considered 

 as invalidating the genus Baptanodon, for on 

 that character alone Marsh distinguished that 

 genus from the European genus Ichthyo- 

 saurus. It would seem better, however, to 

 retain the generic name Baptanodon until 



* ' A New Order of Extinct Reptiles, Saurano- 

 donta,' Amer. ,Journ. of Science and Arts, Vol. 

 XVI., January, 1879, p. 85. 



t ' Fossil Reptilia of the Liassic Formation,' 

 part third, p. 124. 



