CHEMNITZIA. 421 



nence, a pyriform red- brown or yellowish obliquely striated 

 operculum. 



There being some inaccuracies in my account of the C. 

 acuta in the ' Annals ' referred to above, I have reproduced 

 it; as it is an important species embracing several others of 

 doubtful parentage and some varieties, which latter produce 

 the three following distinct forms. The slender subcylindrical 

 variety passes in all collections for the coralline zone C.pli- 

 cata ; this is an error : an examination of the animal shows 

 it to be a C. acuta, differing materially in its organs from 

 the true " plicata" which is essentially a littoral animal, 

 rarely, if ever, found beyond that limit : I have hundreds of 

 examples taken alive. The next form is that of the common 

 livid flesh or pearl-coloured glossy shell of 5-6 volutions, 

 with a cone of broader basal dimensions. This is the type, and 

 though usually smooth in the aperture, is sometimes furnished 

 with transverse crense in the throat. I have four which were 

 examined alive in comparison with the smooth ones, and they 

 are, both in shell and animal, identical; it is difficult to 

 account for the occasional presence of distinct crense in the 

 same species. The third form is of the larger size of 6-8 

 volutions with white shells ; these are smooth, though some- 

 times furnished with striae in the throat of the aperture; 

 I have several of each, which are so exactly represented by 

 the figure of Mr. Alder's O. conspicua in the ' British Mol- 

 lusca/ that I am induced to consider that species as a large 

 crenated C. acuta; and it is not improbable that the 

 O. striolata of the same author, like the C. turrita, may 

 be a striated C. acuta, which are all more or less furnished 

 with spiral striae on the volutions. I must observe, that the 

 crenated examples of C. acuta must not be confounded with 

 any variety of C. conoidea, as the animals of the two are very 

 different ; and as regards the shell, the cone of the one atte- 

 nuates suddenly, whilst in the C. conoidea it diminishes more 

 gradually and tumidly. 



The C. acuta is by far the most abundant Chemnitzia of 

 the South Devon coasts, and is taken in the coralline and 

 muddy shelly districts. Independent of the three principal 



