Cooper.] ^"^ [May 1G, 



under varying conditions, and are thus (indistinguishable from examples 

 of J. niger. Of the value of the differences in jaws and teeth, it will re- 

 quire comparison of many from various localities to decide. 



The species however, is A. andersoni W.6.B. not Prophysaon ander- 

 soni J. G. Cooper, sp. 



Living specimens of these forms differ from A. niger only in pale colors, 

 but all the slugs vary so much in this that it is an unreliable character. 



PnopHYSAON W. G. Binney. 



The figure given of P. hemphilli, represents exactly the alcoholic ap- 

 pearance of my Avion? andersoni (p. 236), and the description is con- 

 formable, allowing for difference in this respect. Still the internal differ- 

 ences observed, may distinguish the northern form until fully compared 

 with the southern. 



In my MSS. description, I remarked on the differences from Avion, and 

 suggested the name Limaoarion, which some friend suppressed in printing, 

 probably thinking it preoccupied. I still have specimens so labelled at the 

 time of writing. At an} r rate Prophysaon andersoni has priority, as a 

 specific name over P. hemphilli. 



On p. 239, Mr. Binney refers to the fresh specimens sent by me to him, but 

 tries to find a discrepancy in m3 r statement that it has a caudal mucous 

 pore. I still think that it has one, but so small as to be imperceptible when 

 contracted by alcohol. This "mucous pore" continues to be a great 

 stumbling block in classification, although it only differs in degree of de- 

 velopment in various genera. All of them are covered with mucous glands 

 as in Limax, each gland with a pore opening externally, and the caudal 

 gland merely varies in size. No more mucus is produced by Ariolimax 

 than by a Prophysaon or Umax of the same size. The large cavity under 

 the mantle as figured by Binney, is rather a notch between it and the end 

 of the foot, than the opening of an enormous gland. In describing Avion 

 foliolatus, Dr. Gould calls it a pit which tends to prove that form to be 

 an Ariolimax. 



Besides this character the position of the spiracle in my figure of A. ? 

 andersoni was t sufficient to prove to Mr. Binney that it was not an Ario- 

 limax, so that there was no need of making confusion by applying the 

 name of my species to one of that genus. 



The number of ribs on the jaw seems variable with age, and as I de- 

 scribed the largest specimens, I found more than given by Binney in any 

 of them. In some cases also, two or more ribs appear consolidated into a 

 wide one, and the lateral ribs are rudimentary. 



In quoting my locality of Santa Barbara for A. columbianus Mr. Binney 

 does not consider that I afterwards separated A. calif ornicus from that 

 species, and that the extreme southern specimens are most likely to be 

 the latter, if not a new form. 



