348 PROCEEDINGS OF THE ACADEMY OF [1896. 



alcoholic specimens in Brit. Mus. The only diagnostic words of 



Cockerell's description are the locality, " Costa Rica." The other 



characters mentioned in the description are common to Columblanus 



and some CaUfornicus. Measurements, etc., as given therein, look 



well on paper, but every practical limacologist knows them to be 



merely an empty form. We consider Cosfaricensis as probably a good 



species, on account of its locality (if correct), but a diagnosis is still 



wanting. 



Genus APHALLARION P. & V. (n. g.). 



External characters, jaw, radula and digestive tract, shell, and 

 general internal topography, as well as female genitalia, as in Ario- 

 Itmax; jjenis (and its retractor') completely wanting, a small and 

 short epiphallus lying in its place ; right eye retractor passing to the 

 left of the genitalia. 



We institute this new group for a large slug like Arion and Pro- 

 physaon in the total lack of a penis and its appendages, and like 

 Ariolhnax in the other essential features, internal and external, ex- 

 cept the disposition of the eye-retractor mentioned above. 



In view of the high development and complicated structure of the 

 penis in ArioUmax, the strength of its retractor, the large size and 

 extraordinary introverted character of the epiphallus, we can hardly 

 refuse generic rank to a form differing so radically as this one. The 

 anterior position of the genital foramen in Aphallarion, the poste- 

 rior position of its breathing pore, and the anterior ovotestis, pressed 

 against the base of the albumen gland, deny to our slug entrance into 

 Arion ; and in the genus Prophysaon the whole internal topography® 

 as well as the type of digestive system is profoundly different. 



A. Buttoni P. *. V. (n. sp.). PI. XII, figs. ?,, 4, 5. 



Color of alcoholic specimens light yellow-brown, the shield lighter, 

 more yellowish, especially anteriorly. Foot-margin dusky, with close 

 vertical black lines, alternately heavier, and seen under the lens to 

 be impressed and pigmented wrinkles. Sole gray, more or less 

 dusky. Anterior third of the mantle free. Length 82 ; length of 

 mantle 34 ; greatest breadth of sole 21 mm. 



Shell oblong, nearly flat, well calcified ; white below, with a 

 yellowish cuticle above, except toward the middle. Length 12 j, 

 width 6| mm, 



®By this we mean the positions of the organs in the body-cavity, both rela- 

 tive and actual. The relative positions of genitalia and digestive tract are 

 greatly varied in dill'erent genera of slugs, and of considerable systematic 

 value. 



