Mr. J. Alder on new species q/Rissoa and Odostomia. 325 



lip slightly expanded, with a large and strong rib at a short di- 

 stance behind it. Inner lip reflected a little at the base, but not 

 unibilicated. The inner margin of the aperture as well as the 

 tip of the spire are generally of a dark purplish brown or violet- 

 colour. Length 2~ tenths of an inch ; breadth one-tenth. 



A variety is marked with zigzag brown lines. 



Procured from small sea-weeds collected in Torbay, where it 

 appears to be tolerably abundant. 



My specimens agree wdtli a foi-eign one of Rissoa costulata, 

 Risso, named by M. Michaud, and kindly presented to me by 

 W. Thompson, Esq. of Belfast. 



Rissoa rufilahrum. Plate YIII. fig. 10, 11. 



Alvania rufilabrum, Leach, MS. Bi-it. Mits. 



Shell ovate, rather broad and thick, tapering to a pretty acute 

 point, yellowish white or brown, more or less tinged with violet ; 

 with seven rather flat w^horls; the upper ones smooth, two or three 

 of the lower with about twelve strong ribs. The ribs are fre- 

 quently only observable on the penultimate and a part of the last 

 w^horls, always disappearing before they reach the lip. The whole 

 surface of the last whorl is covered with punctures formed by the 

 crossing of obscure longitudinal and transverse lines. The spaces 

 between the ribs are coarsely striated. Aperture roundish oval, 

 slightly angulated above, generally of a violet or purplish brown 

 colour, and having a very broad white rib behind it. Inner lip 

 slightly reflected on the pillar, without umbilicus. Length scarcely 

 two-tenths of an inch ; breadth one-tenth. 



Specimens of this interesting species fi-om Brighton have been 

 in my cabinet for several years, and I lately detected one or two 

 among some small shells obligingly sent me from Torquay by 

 Mrs. Griffiths. Dr. Farran of Dublin, to whom I am also in- 

 debted for specimens, found it in some abundance at Connemara 

 in the west of Ireland, 



This species nearly resembles the R. violacea of Desmarest, but 

 is shorter and thicker, and without the spiral band. I have 

 adopted the manuscript name attached to specimens in the Bri- 

 tish Museum. The same species, unnamed, is also in the museum 

 of the Jardin des Plantes at Paris. 



Rissoa? glabra. Plate VIII. flg. 1, 2, 3, 4. 



R. glabra, Brown, Illust. Conch. 2nd ed. p. 13. 



8Ae// ovate-conical, white, smooth, very glossy and diaphanous, 

 with four or four-and-a-half rounded and well-defined whorls, 

 terminating in a rather obtuse point ; the last whorl occupying 

 about two-thirds of the length of the shell. Apertm-e roundish 

 ovate, entire. Outer lip thin, without rib. Inner lip slightly 

 reflected on the pillar, forming a subumbilicus. Length scarcely 

 a twelfth of an inch ; breadth half its length. Opercuhun horny. 



