154 IJTTORINIDiK. 



the shell is about twice its breadth, yet is rarely three- 

 fourths of a sinijle line. 



" The animal is pale yellow with three longitudinal 

 bands of rich brown on the body, and blotches of the 

 same colour on the cloak, mIucIi, seen through the trans- 

 parent shell in a fresh state, may readily be mistaken for 

 markino'S on the latter. The other characters of the 

 animal are those of the genus of which it constitutes the 

 type/' — Alder. 



It was discovered by Mr. Alder and communicated by 

 him to the British Association at Cork in 1843. He 

 found it on small sea-weeds in pools at Dalkey Island, 

 near Dublin, and at Cullercoats, Northumberland. It has 

 been taken, also, in the Channel Isles by Mr. Barlee, who 

 has also found it at Arran Isles, County Galway, at Staffa, 

 and at Lerwick. Mr. Jeffreys has taken it at Langland 

 Bay, near Swansea. 



J. oPALiNA, Jeffreys. 



Subglobose, of throe whorls only ; body greatly longer than 

 the spire. 



Plate LXXVI. fig. 3, 4. 



Rissoa? opalina, Jeffreys, Ann. Nat. Hist, (new series) vol. ii. p. .351. 



Although so minute, and composed of so few volutions, 

 this little shell presents the aspect of maturity. 



It is of a globosely oval form, is extremely thin, diapha- 

 nous, perfectly smooth, and of a peculiarly shining, and 

 sometimes iridescent, uniform brownish white. There are 

 but three whorls, of which the first is moderately large and 

 bluntly mamillary ; the second very convex or even ventri- 

 cose, but mnch shelving, and more than twice as broad as 



