THE NAUTILUS. ; 127 
special generic character, the caudal mucus pore, is lost. This, how- 
ever, undoubtedly existed, for it is indicated in Gould’s description, 
and Mr. Binney informs me that it is present in the examples of var. 
hemphilli from the banks of Chehalis River. Hence the slug cannot 
be a Prophysaon, and the question arises, is it an Arion? From the 
peculiar reticulation, the position of the genital orifice, the shape of 
the penis-sac, and the general character of all its parts, I think we 
may safely say that it cannot be placed in Arion, nor does it agree 
with any other described genus. We have therefore no option but 
to propose a new generic name for it. 
Phenacarion! n. g. 
Animal limaciform, tapering, resembling a Prophysaon, but 
possessing a caudal mucus pore or pit. Respiratory orifice on right 
anterior side of mantle, about one-third of its length from the ante- 
rior border. The mantle conceals a thin and subrudimentary cal- 
careous plate, easily fractured. The sole is not differentiated into 
parts. Genital orifice behind right tentacle. Jaw with numerous 
ribs. Penis sac elongate, cylindrical, thick, not tapering. 
The mantle of Phenacarion foliolatus is quite long, with the shell 
situated near the respiratory orifice. There are black markings and 
spots as figured by Gould. The body has large elongate or 
irregular reticulations, the interspaces being minutely reticulated to 
give the foliated effect on which the specific name was based. The 
edge of the foot has dark transverse lines, alternating with paler 
lines, much as in Arion ater. The sole is transversely and some- 
what obliquely grooved, but there is no separate locomotive disc. 
The jaw has about 23 ribs, denticulating either margin. The 
genitalia are much like Prophysaon, and decidedly different from 
Arion. The testicle (ovotestis) is somewhat subdivided. The vas 
deferens enters at the end of the penis sac. 
Mr. Binney’s notes concerning the typical P. foliolatus give 
“general color of animal reddish-fawn, also of reticulations. On 
the lower edge of the mantle, along the back from end of mantle to 
tail, and above the edge of the foot, is a lighter band, and also on top 
of neck almost to base of tentacles. The light band on edge of 
mantle is irregularly speckled with reddish dots. Mantle minutely 
tuberculated. The oblique perpendicular lines on edge of foot 
alternate wide and narrow.” 
1 phénax—an impostor; Arion. 
