236 PROCEEDINGS OF THE ACADEMY OF [1898. 



eye retractor is not involved between the $ and 9 branches of 

 genitalia ; " retensor " inserted nearer the median line anteriorly. 

 Penis retractor wanting, but several vaginal retractors (fig. 67, 

 vag. r.) arise from the diaphragm. 



Pallial region as in Ariolimax, except that the kidney is larger, 

 and both auricle and ventricle are concealed therein (PI. XV, fig. 

 76). 



Aphallarion is intimately related to Ariolimax, from which it dif- 

 fers in the absence of a penis and its retractor, in having the right 

 eye retractor free from and to the left of the genitalia, and in hav- 

 ing both chambers of the heart embedded in the kidney. No other 

 genus is nearly allied. 



To our former account it may be added that Mr. Wetherby in- 

 forms us that his Ariolimax Hecoxi from Santa Cruz is specifically 

 the same as our A. Buttoni. As he remembers the genital system, 

 it corresponded with that of our species. Since A. Hecoxi was not 

 described, this will in no way affect nomenclature, but is of interest 

 as removing a doubtful species from slug literature, and extending 

 the geographic range of Aphallarion. 



Genus HESPERARION Siuiroth, 1891. 



Hesperarion Simroth, Malak. Blatter (n. F. ) XI, Heft 2, p. 109. Type 

 Ariolimax niger Coop. 



Slugs with the usual small, anterior, shield-like mantle, completely 

 buried, non-spiral shell plate, and long body-cavity excavated to 

 end of tail. Breathing pore somewhat behind middle of right 

 mantle edge. Genital orifice distant from tentacle, below the ante- 

 rior margin of mantle. Foot with longitudinal grooves, becoming 

 oblique on the sides, the foot margin moderate, pedal furrows deep, 

 meeting in a very conspicuous, subtriangular, posteriorly guttered 

 tail pit. Sole rather indistinctly tripartite, the areas not defined by 

 longitudinal grooves. Jaw with coarse ribs. 



Radula with the usual tricuspid central and bicuspid lateral 

 teeth, ectocones small ; marginals with very long, oblique cusps, the 

 ectocone minute or vestigial. 



Intestinal tract (PI. XI, fig. 33) much as in Ariolimax. G 1 in- 

 distinctly divided into crop and stomach, making a half revolution ; 

 G 2 describing a complete revolution in the opposite direction, G 3 

 another, reversed, and G 4 still another revolution parallel to G 2 . 

 Posterior loop formed by G 3 and G 4 lying behind that formed by 

 G 1 and G 2 , as in Ariolimachm generally. 



