THE NAUTILUS. 127 



special generic charactei", 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 f 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 Avion, nor does it agree 

 with any other described genus. AVe have therefore no option but 

 to propose a new generic name for it. 



Phenacarioni n. g. 



Animal limaciform, tapering, resembling a Prophysaon, but 

 possessing a. caudal mucus pore or pit. Resjiiratory 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 foliokttus 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. foliolatiis 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 baud 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 phenax=an impostor ; Arion. 



