DECEMBER 5, 1902.1 XCIENCE. from Mrs. J. M. Arms, who is in charge of In general form and surface markings they nature study in the schools of Boston, Nass.: resemble very closely the teeth of the Liassic Nature study is simply the study of na- Ichthyosaurs of England and Europe. The ture, not the study of books. It is a course teeth were undoubtedly loosely fixed in the of nature lessons especially adapted for ele- jaws knd have been lost in all previously dis- mentary schools. Minerals, rocks, plants and covered specimens. In the present skull a animals are the necessary materials for such few of them have fortunately been retained, lessons. The method of study may be ex- and we have here the first evidence of their pressed in three words, observation, compari- presence in Baptanodon, which may be re- son, inference. The child must be made to garded as the American representative of the see the object he looks at, and to this end he Ichthyosaurian reptiles. tries to draw it and to describe it in writing. When the skull is entirely freed from the Comparative work is mental training, which, matrix and the jaws separated from one an- combined with the observational training other, more teeth will doubtless be exposed. already spoken of, gives a certain degree of From the above evidence it would appear mental power. This power gained in the that the generic terms Baptanodon (Xaurano- early years increases with continued effort. don) of Marsh * are misnomers. Fortunately, this work is recognized as one of The reduction in size and number of the the potent agencies in producing efficient men teeth in the Jurassic Ichthyosaurians is par- and women equipped for a life work that shall alleled in some of the recent Cetacea. Most make for the betterment and enlightenment of if not all of the early (Eocene and Eocene) humanity. cetaceans were well provided with functional teeth, while in many modern forms these HHORTER ARTICLEH. either have been entirely lost or have become DISCOVERY OF TEETH IN BAPTANODON, AN ICH- rudimentary, in some instances appearing THYOSAURIAN FROM THE JURASSIC OF only in the embryonic or young stage of the WYOMING. indivi-dual. Just so the early Ichthyosaurs AMONGthe vertebrate fossils collected by were provided with an abundance of teeth, Mr. 0.A. Peterson during the season of 1900 but in later forms the number and size of the on Sheep Creek, Albany County, Wyo., there teeth were reduced, until in Baptanodon a 'was obtained from the lower beds of the Ju- form was developed which, while still possess- rassic a very conlplete skull of an Ichthyo- ing teeth, was practically edentulous. saurian reptile (Baptanodon discus?) together Ichthyosaurus longirostris as described by with a few vertebm and ribs. Owen,+ was in this respect intermediate be- Through the courtesy of Mr. J. B. Hatcher, tween Ichthyosaurus longifrons from the Lias curator of the Department of Vertebrate of England and Europe, and Baptanodon dis- Paleontology of the Carnegie Museum, this cus of the American Jurassic. material has been placed at the disposal of The presence of teeth, though undoubtedly the writer for study and description. reduced in number and in size in American Heretofore the American Jurassic Ichthyo- Ichthyosaurians, may perhaps be considered saurians were supposed to be edentulous, but as invalidating the genus Baptanodon, for on while preparing thih specimen (No. 603) for that character alone Marsh distinguished that study the remarkable discovery was made that genus from the European genus IchEhyo- the jaws 'bore teeth, two of which were found saurus. It would seem better, however, to between the jaws near the end of the snout. retain the generic name Baptanodon until One tooth was apparently in position in the "'A New Order of Extinct Reptiles, Saurano- upper jaw, while the other lay imbedded in donta,' Arner. Journ. of Bcience and Arts, Vol. the matrix between the jaws and entirely de- XVI., January, 1879, p. 85. tached from them. The teeth are small, t ' Fossil Reptilia of the Liassic Formation,' conical, and covered with longitudinal strize. part third, p. 124. SCIENCE. [N. S. VUL. XVI. No. 414. it has been conclusively shown to be gener- CURRENT NOTES ON PHYSIOGRAPHY. ically identical with Ophthalmosaurus or Ich- RIVERS OF SOUTH DAKOTA. thyosaurus. On the other hand, some may THE 'I-Iydrographic I-listory of South Da- eontend that the present specimen is dis- kota,' by J. E. Todd (Bull. Geol. Xoc. Amer., tinguishable generically from Baptanodon, XIII., 1902, pp. 2740, maps) summarizes the although the writer at present does not believe work of some ten years in serviceable form. this. l'lie general eastward slope from the Rocky Should further studies or future discoveries mountains and Blacls hills (whether result- demonstrate the present specimen to pertain ing from the tilting of formerly level lacus- to a distinct genus and species, it might then trine strata, or from the slant of fluviatile be very appropriately called 1Microdontosnur.?ls deposition) deternlined the delivery of six petersonii, and should those forms previously east-flowing streams to a preglacial geosyn- described by Marsh still prove to be edentu- clinal south-flowing trunlr river whose course lous this character would alone be sufficient is roughly represented by James river in to distinguish it generically from Baptano- eastern Dalsota and by the existing Missouri don. To definitely distinguish it, however, further south. The broad James valley was from Ophthalmosaurus is at present not pos- invaded by a great ice lobe, 1,000 to 2,000 feet sible, and the American and European forms thick, in the latest (TVisconsin) epoch of the may yet prove to be generically identical. glacial period; the east-flowing streams were This discovery is of further importance thereby obstructed, with the result of produ- from a geological standpoint. The existence cing temporary lakes whose combined south- of forms so similar in beds which in America ward outlets across the preglacial interfluves have been referred by Marsh and others to deternlined the Xissouri river in Dalrota. the lower Jurassic and in England and Europe Evidence of the changes thus involved is found in the abundant moraines on the pres- to the Liassic is of the greatest value for pur- ent divide between Missouri and James, in poses of correlation, and if it does not dem- the maslred extension under these moraines onstrate the equivalent age of these two de- of the preglacial east-sloping valleys and posits it at least furnishes additional evidence their interfluves, in the shore lines of various in favor of the Jurassic age of the conform- temporary lakes, and in the apparently ably and immediately overlying Atlantosaurus younger form of the Missouri valley where beds of Marsh, as mas consistently maintained it cuts through the intelduves, although but by that author. few details are given on the latter point. The The points it is desired to emphasize in associated changes in several other rivers are this preliminary paper are : traced. 1. The presence of Ichthyosaurians with ARGESTISE-GI-IILEAN BOUNDARY. teeth in the American Jurassic. 2. The great similarity and perhaps generic A amraRriaBLE report by the Argentine identity of Baptanodon and Ophthalmosaurus. commissioners on the Argentine-Chilean 3. The further evidence it affords in favor boundary has been presented to the British of the Jurassic age of the Atlantosaurus beds arbitration tribunal. It consists of five of Jirnrsh, which has been seriously questioned quarto volumes, printed for the Argentine government by Clomes (London, 1900), with by some authorities. numerous photographic plates and maps, from This material will be more fully described which a great amount of geographic and and illustrated in a paper now in preparation physiographic information may be obtained. by the present author. The dispute that the arbitration tribunal is CI-IARLESW. GII~MORE. to settle turns, as is not infrequently the case CAXXEGIEMUSEUM, in such disputes, upon an insufficicncy of November 1.3, 1902. physiographic detail in the description of