410 PYEAMIDELLID^:. 



Chem. rufa, is acknowledged as a distinct species in the Ap- 

 pendix of the ' British Mollusca.' The Chem. Sandvicensis, 

 the dolioliformis, nonnull., is an old, well-known, accredited 

 species of Walker, Test. Min. Har. We have observed it for 

 the last forty years. 



Nothing is more common than a littoral and coralline zone 

 variety of the same species ; these, from the effect of light, 

 air, sun, habitat, and depth of water, are often so strongly 

 marked as to induce conchologists to convert them into spe- 

 cies, whereas, if they had examined the animal, they would 

 have escaped the mortification of retractation. 



Sometimes the littoral shell is the larger, and sometimes the 

 coralline zone variety. The C. truncatula recently redisco- 

 vered by Mr. Barlee, at Plymouth, is large and elongated in 

 the deeper zones ; but the littoral variety, as with C. pallida, 

 is dwarfish, more slender, and is called by recent authors 

 C. cylindrica. They are undoubted varieties of each other, 

 and both are the Turbo nivosus of Montagu ; with me, Chem- 

 nitzia nivosa. As proof, the learned authors of the ' British 

 Mollusca' have, on the highest authority, pronounced the 

 C. cyhndrica to be the " nivosa " of Montagu ; it follows, that 

 the C. truncatula, which, without question, is the adult of 

 C. cylindrica, is also the " nivosa " of Montagu. A careful 

 comparison of the opercula of the two has since fully con- 

 firmed this view. 



These are the causes that have produced so many spurious 

 species ; we need only instance the Chem. pallida of Montagu, 

 the parent of the following Odostomia eulimoides, 0. rissoides, 

 O. notata, O. albella, O. dubia, O. alba, O. nitida, 0. glabrata. 

 The discovery of the animal of Mr. Alder's Chem. obliqua 

 enables us to say, that the Chem. diaphana of authors is the 

 young of that species. The Chem. Warrenii, called by some 

 the decorata of Mr. Bean, is very distinct, both as to animal 

 and shell, from the "obliqua"; and Montagu's Chem. in- 

 sculpta is well distinguished from both, as our account of the 

 animals of the three will show. With respect to Mr. Alder's 

 Chem. conspicua and C. striolata, we have stated our opinion 

 in the notes on Chem. acuta. 



