Natural Sciences of Philadelphia during the Year 1824, 441 



to ascei'tain that while it belonged to the genus Plesiosaiirus, 

 it must, from its magnitude and the proportion of its parts, 

 have constituted a distinct species. This paper contains also 

 some observations on the manner in which the ribs of the dif- 

 ferent genera of the Saurian family are articulated. He like- 

 wise notices the teeth of several species of sharks : of these 

 teeth, two, belonging to the Squalus carcharias, measure five 

 inches in length, and four in breadth at their base ; and, al- 

 lowing that the fossil animals were proportioned Uke the re- 

 cent ones, indicate that the individuals to which they belonged 

 must have exceeded forty feet in length. 



But the most extensive communication in this division of 

 science is " Mr. Say's account of some of the fossil shells of 

 Maryland," which were collected by Mr. Finch, who expects 

 to describe the geological circumstances under which they are 

 found. Mr. Say's descriptions include about forty new species, 

 besides a notice of several others previously described by him- 

 self and other authors. 



Every thing which connects itself with the histoiy of that 

 large animal which at one time ranged over our country, antl 

 whose bones have been found in many very distant places, is 

 of such general interest, that the " Description of the Os 

 hyoides of the Mastodon," by Dr. Godman, cannot fail to give 

 gratification to all who are anxious to see the structure of this 

 gigantic animal fully illustrated. The description of the bone 

 is full, and acquires some additional interest from the fact 

 that " the whole of the basis, appendix and cornu, have not 

 been fossilized, but stiU retain the characters of bone." 



^ 3. Mineralogy. 



Dr. Troost is the principal contributor to this department, 

 having read to the Academy four papers, three of which have 

 been published, and the fourth will probably soon be so. This 

 author's first communication refers to the petalite, a mineral 

 which had not yet been found in America, but the existence 

 of which was recognised by him in some specimens brought 

 from Lake Ontario by Dr. Bigsby. The presence of lithia in 

 these specimens confirmed their connexion with the European 

 petalite. 



In a second communication Dr. Troost describes, under the 

 name of Unibinaire, a new form of chrysoberyl, which lie ob- 

 served in a specimen from Saratoga, in the state of New York, 

 where it is found in a Pegmatite. The unibinaire " has the 

 appearance of a short hexahedral prism, of which two of the 

 six edges are bevelled." 



Dr. Troost's third communication refers to a new crystal- 

 Vol. 66. No. 332. Dec. 1825. 3 K line 



