244 PROCEEDINGS OF THE ACADEMY OF [1898. 



Whether Seruper's plausible supposition be held to sufficiently ex- 

 plain the self-mutilation of Helicarion or not, it seems to us that the 

 slowness of the process of amputation in Prophysaon precludes the 

 idea that it is a means of escape from birds, which, in any case, are 

 as likely to seize the slug by the head or middle as by the tail. If 

 molluscan foes are in question, the time consumed in amputation is 

 of less moment; and it might be worth while to imprison Prophys- 

 aon with Circinaria (alias Selenites and Macrocyclis), which is the 

 most rapacious snail of the West Coast. The suggestion is offered 

 for what it may be worth ; and the whole subject referred to the 

 enterprising and enthusiastic naturalists of the West for observation 

 and experiment. 



The species of Prophysaon fall into three very distinct groups, 

 two of them containing but one species each, the other including P. 

 Andersoni Coop, (plus Hemphilli B. & B., Padficum and flavum 

 Ckll.), and P. folio latum Gld. (including Phenacarion Hemphilli W. 

 G. B.). As the synonymy indicates, these two species are excessively 

 variable. In the case of Andersoni a great extent of territory is in- 

 habited by the several forms and typical form of the species, and 

 much more extensive series than we have yet seen must be brought 

 together before a final decision upon the limits of variation, and the 

 definable subspecies if any exist, can be made. Our study of them 

 is based wholly upon alcoholic slugs, gathered from localities hun- 

 dreds of miles apart; and it is to be expected that richer collections 

 may modify, and certainly will amplify, the conclusions reached. 



Our general results so far as synonymy is concerned, do not differ 

 radically from those attained by Professor Cockerel], whose synopsis 

 of the species is given below. 16 



16 " (1). Epiphallus stout, sausage-shaped. A pale dorsal stripe. 



a. Ochreous species, P. Padficum (vac\- JlavumY 



b. Grayish species, . . . . P. Andersoni (inch Hemphilli). 

 " (2). Epiphallus banana shaped, but tapering at the end. No pale dorsal 



stripe, . . P- ccBruleum (Epiphallus rather slender, flattish, 

 tapering, somewhat curved. Shell 2 mm. long, narrow, white, 

 shiny).' 

 '(3) Epiphallus slender, gradually tapering to a point. Body with a 

 blackish dorsal band. 



a. Jaw ribbed P. fasciaium. 



b. Jaw only striate, . . . P. humile. (Until more material 

 of Aumi/eis seen, it cannot be made sure that the jaw-character 

 is a specific one.) " 



For some further details of Professor Cockerell's views, see A r atitilus, Nov. 

 1897, pp. 77-79. The "banana" or "sausage" shape of the epiphallus we 

 find to be a variable character, not constant specifically. 



