Mr. W. H. Benson on the Genus Camptoceras. 9 



foreign to our own waters, and it is not improbable that of these, 

 Eunotia quinaria, Ehr., and Nitzschia Palea, Kiitz., will be found 

 to be natives of Britain. There only remains Hyalosira delica- 

 tula, Kiitz., and as Professor Kiitzing gives the Atlantic as a 

 locality for this species, it may also prove to be indigenous. 



This result demonstrates the general distribution of these 

 organisms; and the discovery by Professor Balfour of several of 

 the rarer forms of the Auvergne, among the lofty ridges of the 

 Grampians, is also an interesting circumstance, showing that 

 elevation, and consequently temperature, influence the character 

 of the minute Diatomaceous vegetation, as well as that of the 

 larger and more conspicuous flora of such regions. 



Lewes, Nov. iDth, 1854. 



EXPLANATION OF PLATE I. 



Fig. \. Side views of two valves oi Nuvicula firma, var. /3. 



Fig. 2. Gomphonema capitatum, var. /3. and y. 



Fig. 3. Gomphonema Brebissonii. 



Fig. 4. Gomphonema elongatum. 



Fig. 5. Diatoma vnlgare, var. jS. 



Fig. 6. Diatoma grande. 



Fig. /. Filament and valves of Fragiluria undata. 



Fig. 8. Filament and valves of Odoiilidium anomalum. 



Fig. 9. Achnuntliidium lineare. 



Fig. 10. Achnanthidium coarctatum. 



Fig. 11. Front and side view of Amphitetras antedilutiana, var. (3. 



Fig. 12. Orthosira npinosa : a. Front view from a balsam mounting; 



b. Front view from a dry specimen ; c and c'. Side views of frus- 



tules. 



II. — Amended Characters of the singular Lymneadoiis Genus 

 Camptoceras, ajid desmption of a new Ancylus, inhabitants of 

 Noi-th-western India. By W. H. Bexsox, Esq. 



Ix 1842, M'Clelland's 'Calcutta Journal of Natural History' 

 contained the description of a new Lymneadous genus, which 

 appears not to have attracted in Europe the attention which it 

 deserves, principally in consequence of the scarcity of the pub- 

 lication in the pages of which it is to be found ; although some 

 pains were taken to make it more generally known by forwarding 

 to Mr. Hugh Cuming, and to the British Museum, from India, 

 copies of the paper and specimens of the shell. The form ap- 

 pears of sufticieut importance to warrant the publication of 

 revised and more extended characters of the genus, together with 

 a few observations on its habits, and the locality in which it 

 occurs, points shortly adverted to in the former notice. 



