1882.J — '•' [Williston. 



Syrphid^, bj'- Dr. S. W. Willis! 'U,'' was presented throiigli tlic 

 Secretary, with a letter from the author, dated Xew Haven, 

 Yale College Museum, May 12, 1882. 



" The Classification of the Ungulate Mammalia " was read b}^ 

 Prof. Cope. 



New nominations, ISTos. 959, 960, 9(31, were read. 



The President reported that he had forwarded a memorial 

 to the President of the New York Senate, in favor of the com- 

 pletion of the Palaeontology of New York. 



Power was given to the Hall- Committee to procure a copy 

 of the portrait of Dr. Geo. B. Wood ; and the President was 

 empowered to fill the vacancy caused by the death of Sol. W. 

 Poberts, a member of that Committee. 



Authority was given the Librarian to purchase Yols. I-XII 

 Transactions of the American Philological Association. 



And the meeting was adjourned. 



Contribution to a 3Ionogrcrp]t of flte NortJi. Amcncan Siirpliidcu. Bij Di\ S. 

 W. Williston. 



{Read hefore the American Philosophical Society, May 19, 1S82. ) 



The Syrpliidse form one of tlie most difBcult families of Diptera to 

 classify. Although composed throughout the world of about one hundred 

 and forty described genera, they present no characters that will decisively 

 distinguish any considerable number. As a natural result, many genera 

 have been loosely formed and more loosely described, until the difficulty 

 in identifying species without the aid of numerous types has become ex- 

 tremely great. The present paper is the result of manj^ hours tedious 

 labor in identifying a considerabl}^ large amount of material wholly with- 

 out the aid of types. Prepared two or three years ago it has been re- 

 written and changed many times ; that it is free from error yet I do not 

 presume to hope, but from my own experience in the difficulties that are 

 met with in working with the aid of books alone, I believe that it Avill 

 materially aid in the study of our species. 



In Osten Sacken's catalogue of American Diptera — a work indispensable 

 to all entomologists — fifty-seven genera are recorded as having been cred- 

 itably recognized from North America. Toxomerus of Macquart I have 

 PROO. AMER. pniLOS. soc. XX. 113. 3l. prixteb august 3, 1882. 



