NATURAL SCIENCES OF PHILADELPHIA. 15 



In nature we find the anh3'drite associated with rock salt. Sup- 

 posing that the deposition of the chlorides of sodium and potas- 

 sium took place under a nioderatel}- high column of saturated 

 water, the pressure exercised by this column would give a satis- 

 factory explanation for the fact that calcic sulphate crystallized 

 as anhydrite. The j)resence of gypsum in the same deposits would 

 suggest a subsequent metamorphosis of the anhydrite into gypsum 

 by taking up water. 



January 21. 

 Dr. Bridges in the chair. 

 Twenty members present. 



Notice of Fossil Vertebrates from the Miocene of Virginia. 

 Prof. Leidy directed attention to some fossils, part of a small 

 collection recently received. They were found imbedded in blue 

 clay containing an abundance of fossil diatomes, among which 

 Coscinodiscus is especiallj^ conspicuous. The fossil vertebrate re- 

 mains consist mainly of vertebrae and teeth of cetaceans, vertebrae 

 of bony fishes, teeth of sharks, and spines of rays. Among them 

 also there is a portion of a humerus of a bird, and several worn 

 teeth of a peccary. Besides these there are specimens which may 

 be regarded as characteristic of the following undescribed species. 



Protocamelus virginiensis. Represented by the lower last 

 premolar, and the first and last molars of an animal about the size 

 of the existing Lama, and intermediate in size to Protocamelus 

 occidentalis and F. gracilis of the tertiai'y of the Niobrara River, 

 Nebraska. 



Tautoga (Protautoga) conidens. Represented by a premax- 

 illary with teeth, and portion of another witli the first tooth. The 

 specimens indicate a much larger species than the living Black 

 Fish Tautoga. The bones and relative position of the teeth ex- 

 hibit some peculiarities. The premaxillary externally is flatter 

 than in the Black Fish, and it appears as if it did not turn 

 down in a hook-like end at its outer extremity. The teeth also 

 are separated by comparativel}'- wide intervals, independently of 

 the interspaces provided for successional teeth. The form of the 

 teeth is the same as in the Black Fish. One of the specimens 

 contains the base of the first large tooth and a row behind of 

 seven other teeth. The other specimen contains tlie first large 

 tooth, which is nearly half an inch in length, but proportionately 

 more robust than in the Black Fish. 



Acipenser ornatus. Founded on a dorso-lateral plate indi- 

 cating an extinct species of sturgeon of medium size. The length 

 or height of the plate is about 2^ inches ; its breadth along the 

 crest is an inch and three-fourths. 



