242 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



SEPTEMBEE 25th, 1870. 



William Macleay, Esq., President in the Chair. 

 The Secretary announced the receipt of a donation from the 

 Rev. Dr. Woolls, M.A., of Part 3 of Dr. Von. Mueller's Educa- 

 tional Collection of Australian Plants. 



The following Papeis were read : — 



Observations on the Genus Risella, by Rev. J. E. Tenison- 

 Woods, F.L.S.,F.G.S.,C.M.R.S., Sydney, Tasmania, and of 

 Linn. Soc, N.S.W. 



Risella is a genus separated from the genus Trochus principally 

 on account of the complete absence of any nacreous character, and 

 according to M. Quoy the sexes being in different animals. In 

 1839, Dr. Gray, in the Zoology of Beechey's Voyage, p. 141, pro- 

 posed to unite such shells with the genus Littorina, but in the 

 following year, in his Synopsis of the British Museum, created a 

 separate genus for their reception, which he named Risella, but 

 gave no definition. Philippi, in the Zeitsch. f. Malac. for 1846, 

 gave a definition of the genus and called it Bembicium. Finding, 

 however, that he had been anticipated in the name, but not in the 

 description, he with great modesty withdrew his generic title in 

 favor of that of Gray in his Handbuch f. Conch, n. Malak, 1853, 

 p. 176. In 1864, M. H. Crosse gave in the Jour, de Conch., p. 

 225, a monograph of the whole genus, in which he l'eviewed the 

 synonomy in an exhaustive manner. He also drew attention to 

 certain peculiarities of real generic value which had escaped pre- 

 vious observers, notably the funiculate thickening of the basal part 

 of the throat. The genus may therefore be characterised as 



follows : — 



G. Risella, Gray, 1840. 



Testa univalvis, spiralis, conica, imperforata, haud margaritacea ; 

 anfr. 6-7, planis, ultimo angulato, scepe acute carinato. Apertura 

 depressa, obliqua, rhombea ; fauce in, parte basali incrassata ; 

 columella simplex, obliqua, scindens ; operculum oblongum, comeum, 

 paucispiratum, nucl. marginato. 



