Mat 8, 1908] 



SCIENCE 



727 



The American forms, moreover, present a 

 higher degree of specialization than is 

 known among the European. As stated by 

 the author in an earlier paper, the plesio- 

 saurs as a group, which at least is of sub- 

 ordinal rank, present sufficiently wide and 

 distinct divergences of structure to warrant 

 their separation into a number of well- 

 marked families, families distinguished by 

 structural characters fully the equivalent 

 of those used in the classification of modem 

 reptiles. Of these families, the author is 

 prepared to define at least three from 

 North America: the Elasmosauridse, char- 

 acterized by the greatly elongated neck, 

 absence of interclavicle and interclavicular 

 foramen, and the broad separation of the 

 coracoids posteriorly, especially; the Poly- 

 eotylidse, by the presence of a large inter- 

 pterygoidal foramen anterior to the para- 

 sphenoid, large interclavicle and interclav- 

 icular foramen, three or four epipodial 

 bones, etc.; the Brachaucheniids, by the 

 broad union of the pterygoids anteriorly, 

 the absence of interpterygoidal foramen, 

 very short neck, etc. He believes that at 

 least two other families will have to be 

 erected for the reception of known forms. 



On the Discovery of Vertebrate Fossils in 

 the Pennsylvanian, near Pittsburgh, Pa. : 

 Percy E. Raymond, Pittsburgh, Pa. 

 In the clay which underlies the Ames 

 limestone the writer has found remains of 

 vertebrate fossils. These fossils have been 

 identified by Dr. W. D. Matthew and Pro- 

 fessor E. C. Case as belonging to amphib- 

 ians, theromorph reptiles and pelycosaurian 

 reptiles. As the horizon from which these 

 bones were obtained is in the Conemaugh 

 series about midway between the top of the 

 Mississippian and the base of the Dunkard 

 series (Permian), it seems probable that 

 these are the oldest reptiles yet discovered. 

 It has been suggested that the beds which 

 contain these fossils are of Permian age, 



but in spite of the affinity of these forms 

 with the Permian species, the preponder- 

 ance of evidence at the present time is in 

 favor of retaining the Conemaugh series in 

 the Pennsylvanian. 



On the Discovery of Pelycosaurian Re- 

 mains in Bocks of Pennsylvanian Age 

 near Pittsburgh, Pa.: E. C. Case, Ann 

 Arbor, Mich. (Read by title.) 



The Lignite of Mississippi: Calvin S. 

 Brown, University Post Office, Missis- 

 sippi. 



This paper described the situation and 

 topography of those portions of Mississippi 

 that are known to be underlain by lignite. 

 The mode of occurrence and geological rela- 

 tionship of the lignite beds were outlined 

 and the character of the material in com- 

 position and its value as a combustible were 

 briefly sketched. 



The Influence of the Tides on the Earth's 



Rotation: T. C. Chamberlin, Chicago, 



111. 



The ultimate purpose of the study was 

 to determine whether changes in the rate 

 of the earth's rotation have been serious 

 factors in its deformation. The problem 

 may be approached from the astronomic 

 and from the geologic points of view. The 

 former are largely cosmogonic and tidal, 

 and the tidal involve the cosmogonic. The 

 inferences from the older cosmogonies in- 

 volve gaseous and molten states, as weU as 

 the separation of the moon from the earth ; 

 and are thus radically different from the 

 inferences drawn from a cosmogonic hy- 

 pothesis which permits a rigid elastic state 

 of the earth from its beginning. The sub- 

 ject is, therefore, open to reconsideration 

 in the light of alternative hypotheses. 



The necessity for treating the tides as 

 the phenomena of essentially independent 

 bodies of water lying in irregular basins on 

 the surface of the lithosphere was shown by 



