1898.] NATURAL SCIENCES OF PHILADELPHIA. 219 



REVISION OF THE NORTH AMERICAN SLUGS : BINNEYA, HEMPHILLIA, 

 HESPERARION, PROPHYSAON AND ANADENULUS. 



BY HENRY A. PILSBRY AND E. G. VANATTA. 



In a former essay 1 we undertook a revision of the Arionid genera 

 Ariolimax and Aphallarion. In the present paper the remaining 

 American genera of Arionidce are similarly treated. 



Profiting by a criticism from one 2 whom all limacologists acknowl- 

 edge as master, we have extended our anatomical observations to 

 the pallial organs, muscle system, etc., with interesting and we 

 believe important results. 



The genera of Arionidse, often scattered even by the great malacol- 

 ogists among Helicid or Limacid groups, now fall into orderly se- 

 quence ; and in the flood of light disclosed by comparative study of 

 the myology, the phylogeny and approximately final classification 

 of the various groups is seen clearly outlined before us. 



Trivial and unsatisfactory as are the external features of slugs, 

 the details of their internal morphology are wonderfully varied. 

 Everywhere there are important characters; and those who starve 

 their souls on a mere study of the genitalia and oral armature miss 

 the best part of the feast. 



Believing with Cope that all the facts of morphology should be 

 taken into account in systematic classification — that " system " is, in 

 fact, an epitome of the total structure, as well as, with certain dis- 

 tortions, a phylogeny of organisms, we have freely used characters 

 from all organs in which we found differentiation, in the construc- 

 tion of our scheme of family, subfamily and generic classification. 



We must again gratefully acknowledge our indebtedness to vari- 

 ous friends and correspondents for material received, and especially 

 to Messrs. P. B. Randolph, J. G. Malone and Fred. L. Button. 

 Slugs have also been received from J. G. Cooper, T. D. A. Cockerell, 

 E. H. Ashmun, Wm. H. Dall, W. G. Binney and others ; and the 

 series in our collection from Henry Hemphill has also been of great 

 service. 



1 Proc Acad. Nat. Sci. Phila., 1896, pp. 339-350, pi. xii-xiv. 



2 Dr. H. Simroth, in Zoologisches Centralblatt, IV, No. 6, March, 1897. 



