7208 MoUusks. 



end. At the lowest spring-tides, perhaps two or three times a year, 

 this rock pool is left entirely dry, but at ordinary spring-tides water 

 remains in it to the depth of two or three feet. At such times the 

 conchologist may reap a perfect harvest. He should go provided 

 with a bucket and a man or boy ; the boy should be sent into 

 the water to gather the weeds, while the conchologist himself washes 

 them in the bucket; the sediment should then be taken home, dried, 

 sifted, and examined at leisure ; the stones of the rock pool and the 

 stones within it should also be carefully examined. Among the 

 shells taken in this rock pool, I may mention the present species and 

 the two other members of this genus, Cerethium reticulatum and 

 C. adversum, Rissoa rufilabrum, R. punctura and R. inconspicua, 

 JefFreysia opalina and J. diaphana, Acmaea testudinalis and A. 

 virginea, Eulenia distorta, Trochus helicinus, Odostomia eulimoides, 

 O. turrita and O. spiralis, Chemnitzia indistincta, Amphisphyra 

 hyalina, &c. 



*L. vincta {Lacuna canalis and L. quadrifasciata, Turho vinctus 

 and T. quadrifasciatus). In rock pools and on Laminarite, not 

 uncommon, but generally small. 



Rissoa stfiatula [Rissoa decussata, Pyramis striatulus, Cingula 

 siriatula). Cumbrae, Smith. Rare among Lamlash Bay shell- 

 sand. 



R. crenulata {Rissoa Cimex, Cingula Cimex). Ayr, Smith ; Lam- 

 lash, Landshorough. I have never met with it in the Clyde, but have 

 received it from the Turbot bank, oflf the Antrim coast, so that it may 

 be expected in the Clyde. 



R. zetlandica. Lamlash, Landshorough. 



R. Calathus {Cingula calathisca). Cingula calathisca is included 

 in Mr. Smith's Catalogue as found at Cumbrae; Lamlash, Lands- 

 borough. 



R, Beanii. Not uncommon among shell-sand from " Lands- 

 borough's Bay," but in a worn state. In a living state it is very rare. 



R. abyssicola ? Dr. Landshorough mentions with doubt a speci- 

 men of this beautiful Rissoa as having been taken at Cumbrae 

 {Lands. Excur. p. 443). It is met with in Loch Tyne. 



R. punctura {Cingula punctura^ Rissoa reticulata). Abundant 

 dead in Lamlash Bay, and alive in the large rock pool at the Allans, 

 Cumbrae ; Ayr, Smith. 



R. costata {Cingula costata). Not common. A few dead spe- 

 cimens dredged at Lamlash ; Ayr, Bute, Smith. 



R. striata {Rissoa m,inutissima, Turbo striatus). Abundant. 



