94 THE NAUTILUS. 



the sculpture (consisting of spaced longitudinal cords, the intervals tri- 

 striate), continuous around the whole circumference of the cylinder. 

 Aperture circular, its diameter averaging 13 mm. For illustrations 

 see Froc. Acad. Nat. Sci. Phi la. 1891.— ff. A. Pllshry. 



FoodofLimn.kid.e. Our fresh-water snails are generally believed 

 to be herbivorous. But they greedily feed upon animal matter when- 

 ever and wherever they find such ; on insects, worms, mollusks (even 

 their own species), flesh of any kind, even when living. A Limncea 

 pcdustris was seen last summer having a small leech (about 3 cm. 

 long and 4 mm. wide) in his mouth ; he slowly drew it in and rasped, 

 while the victim was moving and winding about in vain efforts to 

 escape. This I observed for about half an hour, but had not seen 

 how the snail had caught the worm. Afterward the Limnaea held 

 the leech, its anterior part projecting and constantly moving, firmly 

 in his mouth, not rasping, now resting, now creeping about as usual, 

 for an hour and a half more. At that time I had to go away and 

 when I came back no leech w^as to be seen ; w^hether it was eaten or 

 dropped I do not kno\v. 



When these animals are grazing on stones, glass walls in the 

 aquarium, on leaves, or on each other's shells, they always find a 

 good suj)ply of small animals besides algiie, etc., as anyone knows 

 who has examined those " pastures." — Dr. V. Sterki. 



Additional Mollusks of San Francisco County. Since the 

 list by Mr. Wm. J. Raymond and myself Avas published in the 

 September number of The Nautilus, I have found five more species 

 as follows: 



Limax agrestis Linn. 



Limax maximus Linn. 



Prophysaon Andersoni J. G. C. var. marmoratus Ckll. 



Acmcea fenestrata Nutt. 



Mopalia Wossnessenskii Midd. var. Swmisii. 



Making the total number found up to date, 126 species. But two 

 specimens of Limax maximus have I collected, they being apparently 

 young specimens. — Williard M. Wood. 



Planorbis trivolvis Say, and also other related forms, has a 

 peculiar way of moving on or in sand ; he goes " a step, " as far as he 

 conveniently can, with the shell deep down and close to the head ; 

 then he pushes it forward and upward, thus shoving the sand away, 

 and making room for another "step." It is more than probable 



