36 MARSHALL : ON THE BRITLSH SPECIES OF BUCCINUM, FUSUS, ETC. 



These variations and mutations are without end, and all graduate one 

 into the other. The form, texture, size, sculpture, etc., appear to 

 depend entirely on habitat, and an experienced collector can readily 

 tell, from the appearance of the specimen, the nature of the sea-bottom 

 and the probable depth from which it had been procured. The Rev. 

 Professor Gwatkin gives the radula of BurHnum a very bad character 

 as a help to specific distinction; he writes me that "the radula varies 

 so much in Bucrinuin that consider it, for that fq,mily, worthless as 

 a character, the individual variations being greater than the specific." 

 B. undatwu is very scarce in the Channel Islands except at one part 

 of Jersey facing the French coast, and I have never met with a speci- 

 men from the other Islands ; it is equally scarce in the Scillies. Pure 

 white specimens occur occasionally, but they are rare. 



Var. _ffe.ruom, Jeffr. — Very variable in size and texture, sometimes 

 attaining a length of 5|-in. in the West Orkneys and off Wick, 

 while a small thin form lives in the former district and in the Shetlands 

 with the var. zetlandira, and has the same silky epidermis. 



Var. litforalk, King. — The interior of this variety is sometimes 

 orange coloured, but more frequently purplish-brown. 



Var. ijaiqx'rcula, Jeffr. — Specimens from Southampton W^ater do 

 not exceed an inch in length ; iiany are smaller. 



Var. sfrlafa, Penn. — Off Cork Harbour (Wotton) ! off Aberdeen, 

 (Simpson) ! North Rona, 45 f. ; Doggerbank, 30 f. 



Var. pdcKjica, King. — Aberdeenshire (Simpson) ! off Unst 

 (Coulson) ; Shetlands (coll. Mac Andrew). In this variety the last 

 whorl is smaller and narrower proportionally, hardly projecting beyond 

 the penulti;nate, and in British specimens the longitudinal ribs are 

 evanescent or wholy wanting. My largest examples exceed 6|-in. in 

 length. It occurs in Norway, but of a smaller size and strongly ribbed. 



Var. zeflandka, Jeffr. — Gwyn Jeffreys has described this variety as 

 "destitute of ribs," whereas he figures it with rather prominent ones, 

 and this has given rise to some doubts as to whether the var. zetlandka 

 is ribbed or not, especially as he compares it with B. luwqiJireysianum, 

 which is ribless, while this is rendered more confusing by its living on 

 the some fishing-grounds with a dwarf and thin form of var. ^fie.ruosa, 

 which is ribbed, in the Orkneys and Shetlands. But the real truth is, that 

 the presence or absence of ribs is not a criterion of this variety, its 

 only permanent characters being that it is dwarfed and thin. It is 

 almost as variable as the type, and really runs into many forms when 

 collected from different parts of the Shetland seas. It is seldom 

 without traces of longitudinal ribs, especially on the upper whorls, and 

 there is considerable variation in the size, comparative length of spire, 



