TROCHUS. 301 



below by the umbilical ridge : outer lip thin and slightly ex- 

 panded : inner lip folded a little back on the umbilicus, and ad- 

 hering to the pillar : inside more or less iridescent : umbilicus 

 large but not wide, funnel-shaped, and completely exposing 

 the whole of the inner spire; it is encircled outside by a 

 strong spiral ridge, which is often beaded, and winds like a 

 staircase into the interior : operculum forming a spire of about 

 a dozen whorls, the edges of which are imbricated and over- 

 lap one another in succession. L. 0-333. B. 0-275. 



HABITAT: Fine sand, mixed with gravel, in 85- 

 95 f., about 25 miles N.N.W. of Burra Firth light- 

 house, Unst. The area in which it occurs appears to 

 be limited to a few square miles. I discovered this new 

 and beautiful species in 1861, while in company with 

 my friend Mr. Waller; and we obtained specimens 

 again in 1864 by dredging on the same ground. Living 

 together with it were Limopsis aurita, Cylichna alba, 

 Buccinopsis Dalei var. eburnea } and other treasures. I 

 do not know any other place, at home or abroad, where 

 it has been found. 



The animal is active and crawls rapidly ; if laid on its 

 back, it twists its foot from side to side, until part of 

 the sole touches the bottom of the vessel, when it re- 

 gains its usual position. Mr. Alder has examined the 

 tongue, and observes that it shows rather a departure 

 from the generic character in the want of the nume- 

 rous slender uncini which other species possess. When I 

 mentioned the unique habitat of this species, it would 

 probably not convey to the minds of my readers in gene- 

 ral what is meant by dredging in Shetland, nor how 

 many difficulties and disappointments beset the natu- 

 ralist who ventures thus to explore that remote and wild 

 tract of the North Sea. The weather is so uncertain, and 

 the winds often so boisterous, even in the summer and 

 autumn months, that, although provided with every ap- 



