78 VERMETID.E. 



on the neck less conspicuous than in the other species : foot 

 carried much more laterally. It is similar in other respects, 

 taking into account the difference of size and greater delicacy 

 of the present species. (Clark.) 



Shell of nearly equal breadth throughout, not quite so 

 much curved as in C. trachea, rather thin, transparent, and 

 glossy : sculpture, none except under the microscope, which 

 exhibits a slightly frosted appearance : colour clear-white : spire 

 replaced by a rounded but not very convex shelly plug : mouth 

 annular, thickened at its edge : operculum resembling an in- 

 verted tea-cup without a handle, yellowish-brown, and consist- 

 ing of about 10 regularly increasing whorls, 6 of which are 

 raised, one above another (like circular steps), and are defined 

 by a narrow spiral ridge ; they are distinct on the crown oi 

 centre, which is depressed. L. 0-075. B. 0-0135. 



Habitat : All our coasts, from Shetland to Guernsey, 

 in the coralline zone ; common. Fossil in the Coralline 

 Crag at Sutton (S. Wood) ; Norway, in newer or post- 

 glacial deposits, 50-80 feet (Sars). Living in Norway 

 (Lilljeborg) ; Mangerfiord, near Bergen, in 10-50 f. 

 (Sars) ; Bohuslan, 10 f. (Malm) ; Danish coast (mns. 

 Copenhagen) ; Brittany (Mace and Cailliaud) ; Provence 

 (Forest, Martin, and Mace) ; Nice (Verany) ; Spezzia 

 (Doria and J. G. J.) ; Canary Isles, 12-50 f. (M f An- 

 drew) . 



" I thought the Caecum trachea very active, but it is 

 far surpassed by this animal ; I put one of each in a 

 watch-glass of sea-water, and with a camer's-hair brush 

 gave them a fair start, but the little one beat its compe- 

 titor hollow, and accomplished a space of 2 inches in 

 55 seconds ; thus affording a proof, even in the Mollusca, 

 that Nature compensates for the small volume of the 

 minute beings in giving them greater energy, vivacity, 

 and quickness/' (Clark.) Half-grown shells are more 

 slender and curved, with a proportionally wider mouth. 

 The spire of the fry has two whorls — the inner one 



