FAMILY LYMN.EACEA. 163 



the three preceding species, Lymncea palustris has a rather more 

 solid, roughly coated shell. The whorls, which are more symme- 

 trically convoluted, increase with the regularity of a Peruvian Buli- 

 mus, and the shell is not unlike one in general aspect. The outer 

 surface is of a dull fuscous-horny hue, sometimes glazed with a clean 

 opake violet-grey coating, promiscuously freckled with dots of a 

 darker grey, while the interior is lined with a thin enamel of warm 

 fuscous red. The animal is mostly dark violet tinged with green, 

 variegated with black and opake white or yellowish specks. It is 

 described by Mocpain-Tandon as being sluggish and irritable, with- 

 drawing its tentacles on the slightest touch, and very voracious. 

 It crawls out of the water, carrying its shell abnost horizontally. 



L. palustris abounds in every part of Europe, reaching south- 

 wards to North Africa, and it appears to be equally common with 

 L. limosa in Siberia, but we have no record as yet of its presence 

 in Cashmere or Thibet. In America it is closely represented by 

 L. elodes of the Northern States, and by L. umbrosa and reflexa of 

 the Western and Middle States. Dr. Gould, while speaking of 

 L. elodes in his ' Eeport of the Invertebrata of Massachusetts,' has 

 some curious remarks on its economy. " The animal," he says, 

 " attains maturity and dies about the end of June. At this time 

 the young may be seen with the old, about an eighth of an inch in 

 length, and these continue to grow rapidly during the season. But 

 after the early part of July, it is rare to find an adult shell con- 

 taining a living animal. At this time the exterior of the shell 

 is much eroded. In fact, the animals, as they cluster together, 

 actually devour each others' shells; the aperture becomes white and 

 sometimes chalky, and the brown submarginal callus of the outer 

 bp is thus covered over." Its European analogue, says Dr. Gould, 

 is L. palustris ; and while alluding to these and to L. umbrosa and 

 reflexa, he adds, " After all, these species are so nearly allied that 

 no description, and, perhaps, no figure will enable any person to 

 determine any one of them by itself. They must be learned by 

 comparison and by interchanging specimens. But the difficulty 

 does not end here. It is no easy matter to assign the limits of a 

 species. No one presents a greater variety. The length of mature 

 shells varies from half an inch to an inch, and it is remai'kable that 

 the largest specimens are usually the most fragile. The surface 

 usually has an uneven aspect, coated with mud." 



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