AXIXUS. 251 



much more recurved; and the tooth-like folds are 

 stronger and more prominent. I at one time thought 

 it might be the young of A. Sarsii ; but having been 

 favoured bv mv kind friends in the North with a series 

 of specimens from several localities, I am enabled to 

 express a positive conviction that my shells are not the 

 young of that species or variety. The shell of A. Sarsii 

 in all states of growth is even more globular than A. 

 flexuosus, the furrows are equally strong (except in 

 large specimens, when they are less conspicuous), and 

 the tooth-like folds are wanting or indistinct. A. Sarsii 

 is usually found in deeper water than A. flexuosus, and 

 I am not aware that both forms have ever been taken 

 together. Asbjornsen gives different localities for each 

 on the coast of Norway ; and Malm informs me that 

 on the Swedish coast he always finds A. flexuosus on 

 softer ground and in shallower water than the other. 

 A. Sarsii attains a much larger size ; and Lilljeborg 

 showed me a comparatively gigantic specimen, which 

 was upwards of an inch long. It occurs in the Udde- 

 valla beds. The authors of the ' British Mollusca ' in- 

 advertently placed A. Croulinensis with A.ferruginosus. 

 The outline of each will be sufficient to distinguish 

 them, independently of other characters. The shell of 

 the former is obliquely oval, and that of the latter 

 almost globular. 



3. A. ferrugixo'sus*, Forbes. 



Kellia ferruginosa, Forbes, iEgean Invert., Brit. Assoc. Rep. 1843, p. 192. 

 Lucina ferruginosa, F. & H. ii. p. 60, pi. xxxiv. f. 1 . 



Shell nearly globular, but more tumid towards the beaks, 

 covered with a thick ferruginous crust or coating like the rust 

 of old iron, beneath which it is thin, opaque, and rather glossy : 



* Covered with iron-rust. 



