PROPHYSAON. 237 



distinct locomotive disk to foot, but crowded, oblique furrows running from 

 centre to edge. Respiratory and anal orifices on the right margin of mantle, 

 slightly in advance of its centre, with the usual cleft to the edge. Genital 

 orifice behind and below, but quite near to the right eye-peduncle. No caudal 

 mucus pore. 



Jaw of the single species known, P. Hemphill^ thick, low, wide, slightly 

 arcuate, with but little attenuated ends, cutting margin without median pro- 

 jection ; anterior surface with 1 5 stout, irregu- 

 larly developed, separated ribs, denticulating Tig. 138. 

 either margin (see Fig. 138). 



Lingual membrane (PI. V. Fig. I) long and 

 narrow. Teeth about 40 — 1 — 40, with 16 per- 

 fect laterals. Centrals with a base of attach- 

 ment longer than wide, reflection extending less > " jaw of P. Hemphilli. 

 than one half the length of the base, with a very 



stout, short median cusp, bearing a stout, short, blunt cutting point, and on 

 either side a subobsolete cusp bearing a stout, bluntly rounded, short cutting 

 point. Laterals like the centrals, but asymmetrical, as usual, by the suppres- 

 sion of the inner side cutting point and inner lower, lateral expansion of the 

 base of attachment. Marginals (i) low, wide, with one inner, stout, oblique 

 cutting point and two outer, smaller, blunt cutting points. 



As in all lingual membranes, there is a difference in the development of the 

 cusps and cutting points on various parts. The teeth figured are the least 

 graceful in their outlines. 



Found in the Pacific Province, in Oregon and California. Mr. Henry 

 Hemphill has collected specimens from Astoria to San Francisco Bay. 



This genus agrees with Limax by having an internal shell, and by the posi- 

 tion of the genital orifice. It differs by its ribbed jaw, by the subquadrate 

 marginal teeth of the lingual membrane, and by the anterior position of its 

 respiratory orifice. The genus is allied to Avion by its ribbed jaw, its quadrate 

 marginal teeth of the Ungual membrane, and by the anterior position of its 



Genus Limaci, Arioni et Ariolimaci affine, sed facile distinguendum. Limaci affine 

 est testa interna, et positione aperturae genitalis ; sed differt maxilla costata, dentibus 

 lingualibus marginalibus subquadratis, et positione aperturoe respirationis. Arioni simile 

 est genus maxilla costata, dentibus lingualibus marginalibus et positione aperturae respira- 

 torins ; sed differt testa interna, positione aperturae genitalis, et poro mucoso carente. 

 Ariolimaci affine est maxilla costata, dentibus marginalibus quadratis lingualibus, et 

 testa interna ; sed differt positione aperturarum, respiratoriae et genitalis, et poro mucoso 

 carente. De omnibus generibus supra comparatis differt etiam nostrum genus carente 

 disco gressorio distincto. 



De genere Hibernieo Ge.omalaco differt carentibus poro mucoso caudali, disco distincto 

 gressorio, et positione pallii et aperturae respiratoriae (in Geomalaco valde anteriore) ; 

 affine est testa interna, dentibus quadratis marginalibus lingualibus, maxilla. 



Ab ceteris generibus Americanis sat distinctum est. 



