THE ANNALS 



>i> 



AND 



MAGAZINE OF NATURAL HISTORY. 



[FOURTH SERIES.] 

 No. 15. MARCH 1869. 



XXIV. — OntJie Animal and Oj'ierculum o/Georissa, W. Blanf.^ 

 and on its relations to Hydrocena, Parreyss ; with a Note 

 on Hydrocena tersa, Bens., and H. milium, Bens. By 

 William T. Blanfoed, A.R.S.M., C.M.Z.S., &c. 



[Plate XVI.] 



In the ^Annals and ]\Iagazine of Natm-al History' for June 

 1864, ser. 3. vol. xiii. p. 463, I pointed out that some small 

 land-shells from the Khasi Hills and Burma, described by 

 Mr. Benson as species of Hydrocena, differed so much in the 

 characters of the animal and operculum from the other forms 

 classed in that genus by Pfeiffer and other conchologists, that 

 it was necessary to found a new genus for their reception ; and 

 I suggested that this genus, which I proposed to call Georissa, 

 might be an ally o^ Helicina, which it resembled in the absence 

 of spiral structure in the operculum. Recently Capt. Godwin- 

 Austen has had oppoi*tmiities of examining living specimens 

 of Oeorissa sarrita, Bens., in the Khasi Hills, and he has very 

 kindly placed his drawings at my disposal, calling attention to 

 one point which I had overlooked : this is the existence of a 

 projection on the inner side of the operculum, somewhat re- 

 sembling that in Rissoina. This projection is so brittle that, 

 unless great care be used in extracting the operculum, it is 

 sure to be broken, as it was in the two or three specimens 

 which I examined in 1864. 



On hearing of this, I reexamined the opercula of the three 

 species of Georissa of which I possessed specimens, viz. G. 

 pyxis, Bs., G.frustillum, Bs., and G. sarrita, Bs., and found 

 the projection in all, varying slightly in form. 



Both Capt. Godwin-Austen and I have also examined the 

 lingual teeth, and found that, although they belong to the 

 Rhipidoglossate type, they differ entirely from those of Ileli- 

 cina and its allies. Capt. Godwin-Austen could detect no teeth 



Ann. cC* Mag. N. Hist. Ser. 4. Vol. iii. 13 



