152 PROCEEDINGS OE THE ACADEMY OP 



indicate its near alliance with L. TrasHi, differing as much, how- 

 ever, as several others of the allied species. 



Specimens said to come from San Luis Obispo appear to be the 

 same, and are the ones referred to by me in the Cal. Acad. Proc. 

 III. 332, as combining characters of ramentosa and Dupeiithouarsi. 

 I am, however, becoming more and more of the opinion that 

 natural hybrids are so very scarce that shells presenting interme- 

 diate characters are to be considered rather varieties in which 

 local proximity and exposure to the same influences produce 

 changes simulating those of neighboring geographical groups, as 

 before remarked, concerning some of our most northern and 

 southern forms. Thus we have in this the nearest approach to the 

 sculpture of the Ariontas to be found in our Lysinoes, as it exists 

 on a belt next adjoining the centre of development of the sculp- 

 tured group. L. Dupelitliouar&i often shows a little of the same 

 sculpture. 



This form probably occupies the whole of the gap of 160 miles 

 south of Mount Diablo, mentioned previously by me as destitute 

 of any known species, but at an elevation seldom visited by col- 

 lectors, though the young specimens, also found by Dr. Yates, " at 

 the crossing of the Salinas River above Soledad," indicate that it, 

 like others, may follow down the river banks into the vallej^s. 

 These have a smaller umbilicus and flatter apex. About two hun- 

 dred miles southward, the Mount Diablo range combines with the 

 coast range near San Luis Obispo, the Salinas Valley lying be- 

 tween them. 



Genus ASSIMINEA, Leach. 



Although not a pulmonate mollusc, the species to be described 

 forms a link between these and the branchiate shells, in its power 

 of existing for several days, and even of crawling actively about 

 in a slightly damp bottle, showing nearly as much vitality out of 

 water as the Alexia with which it lives, while it cannot exist in 

 fresh water. It is probable that, like Amjndlaria, etc., it possesses 

 a reservoir for moistening its gills, or a sort of imperfect lung. 

 Its subterminal tentacular eyes are also similar to those of the 

 Pujnllse, with only one pair of tentacles. 



It will be lucky if some hair-splitting microscopist, ambitious 

 of affixing his name to the species of others, does not find a slight 

 difference in the lingual asperities on which to found a "new 



