Bibliographical Notices. 351 



The perco])tion of these facts led zoologists to direct their attention 

 more cspcciallv to the structure of the molluscous animal, in forming 

 their classifications, and there can be no doubt that this has been 

 attended wdth most beneficial results ; but many of the partisans of 

 the new system, on their emancipation from the fetters of a pure 

 conchology, rushed into the very opposite extreme, regarding the 

 structure of the hard parts as of no value even in the discrimination 

 of the smaller groups. With the usual zeal of reformers, they re- 

 quired that every trace of their former faith should be destroyed ; 

 they tore down the ancient images from the niches in which they 

 had for years commanded respect, but unfortunately in too many 

 cases only to set up new ones in their deserted places. 



In thisL number we must jjlace Mr. Clark, the author of the work 

 whose title stands at the head of this notice. For ^Ir. Clark the 

 structure of the shell is of little or no value ; for although he tells us 

 (p. 239) that he considers " the shell-coverings of the Mollusca as 

 good and useful aids, in strict subservience to the malacology of the 

 animal, and as consequential specialties emanating from the vital 

 organs," he appears generally in the course of his work entirely to 

 disregard the characters derivable from the shell and operculum. It 

 appears to us that Mr. Clark, like many other authors, lays too much 

 stress upon the instances already referred to in which different ani- 

 mals inhabit shells of the same construction. We agree with him in 



regarding the " shell-coverings of the Mollusca as specialties 



emanating from the vital organs," and therefore think that the cha- 

 racters derived from the structure of the shell and operculum should 

 certainly be regarded as of some value in the arrangement of the 

 ^lollusca. Mr. Clark, however, appears to entertain a different opi- 

 nion, and applies the pruning-knife most imsparingly to all groups 

 which he considers to have a purely conchological origin. As an in- 

 stance we may refer to his genus Murex, in which he includes the 

 whole of the species belonging to the genera Murex and Buccinum of 

 Linnseus, which are considered by most authors as forming numerous 

 genera, and by many as constituting at least two families. 



Mr. Clark's primary principle of classification is derived from the 

 sexual relations of the animals, which he describes as Hermaphrodita 

 sine conyressu, Hermaphrodita congressu, and Bisexual; by the 

 latter tei-m we must understand unisexual. This prmciple certainly 

 has not the merit of novelty, which the author appears to claim for 

 it, for his terms as applied to the Gasteropodous Mollusca are ex- 

 actly identical with the Paracephalophora hermaphrodita, moiioica 

 and dioica of De Blainville, and as both the groups of Acephala are 

 defined as Hennaphrodita sine concubitu, it is hard to say what is 

 the advantage of this sexual system. Its cUsadvantages however are 

 more apparent, for when Mr. Clark tells us that the Acephala are 

 hermaphrodite animals, we must regard this statement as a simple 

 assumption in the case of the Palliobranchiata, whilst in regard to 

 the Lamellibranchiata, it is distinctly at variance with generally re- 

 ceived views ; and we look in vain in our author's pages for a satis- 

 factorj' reason for adopting his opinion, — his anatomy of Pholas dac- 



