Mollusks. 2235 



with numerous volutions, the aperture of a young individual bears a greater proportion 

 to the axis of the shell than it does when the animal is fully grown ; and it is not al- 

 ways possible to ascertain when an individual has reached a state of maturity. The 

 form of the aperture is nearly the same at all ages or states of the individual, but the 

 lengthening or shortening of the convoluted cone, which may be the result of external 

 causes, will materially affect any mathematical proportion that may be assumed as a 

 standard for specific determination ; and the spiral angle, or angle of volution* upon 

 which some continental conchologists have placed so great reliance, is a test, in my 

 opinion, equally illusory and deceptive. In Littorina littorea, for example, the varia- 

 tions extend, in what I firmly believe to be individuals of the same species, from a 

 subulate or tapering form of volution, denoting an angle of scarcely twenty degrees, to 

 another form which, by the application of the same rule, would show an angle of 

 ninety degrees ; this may be seen in Plate X., where the figures are by no means ex- 

 aggerated, but rather fall short of the two extremes. A like want of permanent regu- 

 larity in proportionate dimensions is equally exhibited in the Acephala or bivalve 

 mollusks; and minute attention to accurate detail or mathematical proportions is 

 rarely to be depended upon, even in that class. In some species, of which the general 

 form may be considered as transverse, the character may be traced through trifling and 

 almost imperceptible gradations until it is decidedly elongate, so that mathematical 

 proportions in such cases are of no determinate value. This is more particularly evi- 

 dent in some of the species in the Crag formations, where, perhaps, a rather more 

 than ordinary degree of variation may be seen ; and such are the extraordinary varie- 

 ties in many of the species, that no reliance can be placed, for specific determination, 

 upon minute proportionate dimensions, although, as an auxiliary, they may in some 

 cases be usefully referred to." 



The mode in which the author has executed his task appears to me highly credit- 

 able, and the work must at once take rank as one of the most valuable contributions 

 science has received during the year. I would, however, extend a word of advice to 

 the publishers, if by that name I may call the managers of the Society, in whose name 

 the volume is issued : they appear to be at present very raw in all the details of getting 

 out a book, and the result is that the present volume is half-spoiled in the issuing : 

 the binding is a flimsy piece of pasted paper, and yet the edges are cut down as though 

 the book were bound in calf and gilt ; the paper for the plates is not large enough ; 

 and again, the letter-press of such a costly work should have been hot-pressed : these 

 rather important faults arise partially from a false economy, a sort of penny-wise- 

 pound-foolish system, and partly from the absolute want of the requisite trade-know- 

 ledge of these secondary but still essential details. I trust that in future publications 

 they will be reformed. — Edward Newman. 



" * The angle formed by a line drawn from the vertex on each side of the shell, 

 which varies, of course, upon the greater or less depression of the volution, the sutural 

 angle, also, depending upon the same cause." 



