PLATE XCI. 



the centre, and are sulcated longitudinally. There are besides this 

 central ridge, two equally well defined though narrower striae, dis- 

 posed on each side of the central line or ridge, so that each of the 

 longitudinal rays constitute a quintuple series of raised lines, the 

 middlemost of which forms the most prominent elevation, the others 

 lying on the lateral slopes. There can be no hesitation in admitting 

 those shells to be perfectly different, but we have deemed it requisite 

 to point out those distinctions since there is, as it will be perceived, 

 a general assimilation at least, and that our present shell appears to 

 form an intermediate species between the two. 



It will have been observed, that we have laid no particular stress 

 upon the difference that prevails in the colours of those different shells, 

 because among many varieties of those shells it would not be difficult 

 to find examples that would accord, in this respect at least, in a 

 general manner ; indeed, so dissimilar are many of the shells of 

 monoetis in this particular, that the species has obtained the name 

 of varia, and although from the term subrufa, applied to the other, 

 it may be understood as being somewhat rufous_^ we often find it 

 elegantly varied with other colours. Our present shell, it may be 

 added, is more transparent, thinner, and more brittle than either of the 

 former, and the colour dark rufous, varied with purple ; both valves 

 are convex. 



Regarding this as a new species and one to which no name has 

 been hitherto appropriated, we conceive it cannot be assigned with 

 more propriety than to compliment the name and labours of 

 Dr. W. G. Maton, the author jointly with the Rev. Thomas Rackett 

 of a valuable and useful paper on the subject of British Conchology, 



