BY AV. F. PETTERD. 79 



proportion of length to width = 5 : 2. The mouth, 

 likewise occupies 2-5ths. of the whole length (with young 

 specimens it stands nearly vertical) ; the upper angle of the 

 same clings to the preceding whorl and appears rounded off; 

 the columual rim is bent, and closes wholly the umbilicus (iu 

 young examples it does not quite do so). Shell, thin, 

 glistening with lines of growth, brown, like Helix lucida, or 

 brown-red, edges of aperture white in colour. Apparently 

 it occupies the central position between thermalis and acuta, 

 as proved by size and colour, which, however, deviate some- 

 what. (Spiral cover.) 



Discovered by Professor Brauu, in large quantities with 

 Chara macropogon. A. Br. iu Van Diemen's Land." 



" //. Tasmanica. V. Martens. 



Von Fraueufeld, in Trans, of K. K. Zool. and Bot. Soc, 

 page 653. No. 830. Vol. XIV., 1864. 



This has been described by V. Martens, iu Weigmann's 

 Archives, 24, 1, page 185, illustrated on Table V., fig. 12. 

 The reference to " Spiral cover " appears as certainly remark- 

 able." 



Hydrobia cristallina. Pfr. 



This appears to be one of the earlier described species, and 

 judging from the reference made to it, certainly anterior to 

 the next. In the next jiortion of my summary of our aquatic 

 shells I hope to be able to supply the full original diagnosis. 



Hydrobia Gunnii. Frauenfelil . 



"Transactions of the K. K. Zoological and Botanical 

 Society, Vienna. Vol. XIII. No. III. and IV., page 1,025, 

 1863. 



In Cumming's collections, marked by Mr. Gunu, as from 

 Van Diemen's Land, this shell is found intermingled with 

 Hydrohia cristallina Pfr. and likewise Amnicola diemense 

 Frfld. 



It is characterised by its beautifully formed mouth, which 

 is almost without traces of any edge. Shell, slender, conical, 

 grayish-brown in colour, semi-trans]>arent, frequently with 

 6^ turns and confined cicatrix, small opening of mouth, round, 

 with totally free edge which arches or overlaps outwards. 

 Length, 3 mm; tcidlh, 1"5 mm. 



(Frauen field). 



JS. Gunnii, V. Frf. Transactious of the K. K. Zoological 

 and Botanical Soc, Vol. XV., page 526, 1864. 



Distinguished by its equally formed mouth or orifice, the 

 edges of which as standing somewhat apart from the spin- 

 duhvr cell sides makes one to remember it as similar to a 



