Zoological Society. 331 



ZOOLOGICAL SOCIETY. 



March 12, 1850.— W, Spence, Esq., F.R.S., in the Chair. 



The following papers were read : — 



1. On a new species of Lymn^a from Thibet. 

 By Lovell Reeve, F.L.S., F.Z.S. etc. 



Lymn^a Hookeri. Lijmn. testd ovatd, tenuiculd, conspicuh 

 umhilicatd, anfractibus quatuor ad quinque, convexis, supernh 

 depresso-rotundatis, suturis subimpressis, aperturd orbiculari' 

 ovatd, marginibus lamind latiusculd subverticali conjunctis ; 

 sordide olivaceo-fuscd. 

 The above-described freshwater mollusk, collected by Dr. Hooker 

 on the Thibetian or north side of Sikkim Himalaya, at 18,000 

 feet elevation, belongs to the same type as our well-known Lymncea 

 peregra, and affords an interesting addition to the evidence which 

 has been in part collected touching the wide geographical distribu- 

 tion of corresponding fonns of plants and animals over those parts of 

 Europe and Asia where there are no extensive mountain-barriers. 

 The European Lymncea stagnalis has been collected as far east as 

 Affghanistan, and the typical form of Lymneea peregra is very cha- 

 racteristic in this species from Thibet. A depression of the whorls 

 next the sutures, which gives a more orbicular form to the aperture, 

 and a conspicuous umbilicus, which is not in any degree covered by 

 the columellar lamina, prove it to be specifically distinct from Z. 

 peregra ; and these characters do not appear in the various modifica- 

 tions of that species arising out of its more or less ventricose growth, 

 or more or less attenuated convolution. South of the Himalaya 

 range, where Dr. Hooker reckons the snow-line to be 5000 feet 

 lower than on the north side, and 3000 feet lower than the locahty 

 inhabited by this species, the LymncecE are of quite a different type, 

 more especially in the plains of Bengal, where the shell, owing to its 

 being formed in so much warmer a temperature, is of stouter growth, 

 and characterized by some design of colouring. The European types 

 of Lymncea, ranging over Russia and Siberia, appear abundantly in 

 the stagnant waters of North America ; and some are identical in spe- 

 cies. L. elodes of Say, inhabiting Pennsylvania, is doubtless the 

 same species as the European L. palustris ; L. truncatula of the 

 same author appears to be identical with L. desidiosa ; and the L. 

 peregra, represented by L. Hookeri in Thibet, is represented in Penn- 

 sylvania by Say's L. catascopiurn. The Lymncece of Australia are of 

 a remarkable and very distinct type from either of those mentioned 

 above. 



I have much pleasure in naming this Thibetian Lymncea after the 

 indefatigable traveller, whose researches into the natural and phy- 

 sical history of that remote country into which few have penetrated, 

 are hkely to be attended with such important results. I have placed 

 the specimens in the British Museum. 



