NATURAL SCIENCES OF PHILADELPHIA. 507 



November 18^. 

 Mr. Lea, President, in the Chair. 

 Twenty-one members present. 



Prof. Baird communicated the fact that in his recent visit to Philadelphia, 

 he had noticed that the leaves of the Silver Maple in the city and vicinity were 

 dotted with black, indurated spots. Having transmitted specimens to Mr. C. 

 C. Frost, the cryptogamic botanist, of Brattleboro', Vt., he was informed that 

 the spots consisted of the Rhytisma aceris-eriocarpa, Schw. 



Dr. Leidy presented a specimen of syenite obtained from a recent exposure 

 of that rock, among the gneiss on the Schuylkill, at Fairmount Park. He 

 also remarked that he had noticed a boulder, apparently of Potsdam sand- 

 stone, at the corner of Thirty-seventh and Market Sts., which had been ex- 

 posed in digging gravel. It was the largest transported block he had observed 

 in our vicinity. It is oblong square and measures 7 feet long, 32 inches high 

 and 40 inches wide. 



November 25th. 



Mr. Vaux, Vice-President, in the Chair. 



Eleven members present. 



On report of the Committee, the following paper was ordered to be 

 published in the Proceedings : 



Monograph of the Prehensile-tailed QUADRUMANA. 



BY J. H. SLACK, M. D. 



Few departments of mammalogy are less thoroughly understood than that 

 of the American Quadrumana. The great variety of coloration in many species 

 consequent on age and sex, added to their comparative rarity, combine to ren- 

 der their study excessively difficult. Suites of specimens of any species are rare 

 even in the great European Museums. The species of the genus Cebus, perhaps 

 the most common of the American Quadrumana have long been a source of dis- 

 pute among naturalists. Wagner, (Schreber's Saugetbiere, Supplement band, vol. 

 i. p. 207, 1840,) reduces the number of species in this genus to two, regarding 

 the second as doubtful, while Reichenbach, (Die Vollstandigste Naturgeschichte 

 der AffeD, part I.) is content with no less than thirty-seven, not only describing 

 but figuring them ! In the Cebus fatuellus, the young is of a light brown, and 

 the adult of a deep black color, and in the Aluatia niger (Stentor niger, Geoff.) 

 the female and young are of a pale straw color, slightly dashed with black, 

 while the adult male is entirely of an intense black. As such states of colora- 

 tion have been regarded by certain eminent naturalists as specific characters, 

 great confusion in synonymy has resulted. 



In regard to nomenclature, I have followed closely the rule of priority, always 

 adopting the oldest generic and specific names whose applications can be ascer- 

 tained. In regard to the rules given by Isidore Geoffroy St. Hilaire,* (Cat. 

 des Primates, p. xi.,) the first and second are broken by him on the fourth 

 page of the work in which they are promul^f ted ; where the generic name 

 Troglodytes is retained for an animal living among the branches of trees, the 



* Rejeter les noms absurdes par eux memes, ou contradictoires avec les faits ou lee idees 

 quils sont destines a exprimir. 



Rejeter les noms deja employes dans une autre acceptation. 



Considerer comme non avenus (toutfois les citant en synonymie) les noms tombes 

 en desuetude- 



1862.] 



