Zoological Society. 149 



Cuvier, De Blainville, Desliayes and Gray have successively devoted 

 themselves to the subject. In illustration of the progress of Con- 

 chologj^ Mr. Reeve exhibited to the Society a series of written 

 tables, showing the systems of classification and nomenclature pur- 

 sued by these several authors. He observed, that the simple method 

 of Lamarck was that usually adopted, but the last that had been in- 

 troduced was that of Mr. Gray published in the British Museum 

 S}^nopsis. The chief object of this author appeared to be to extend 

 the application of the nomenclature, in which he enumerates more 

 than three times the number of genera mentioned by Lamarck. He 

 could not fail to appreciate many useful alterations in Mr. Gray's 

 system of classification, and thought it was entitled to considerable 

 merit on account of the attention vv'ith which he had studied the 

 animals ; he could not however but express his fears that many of 

 Mr. Gray's changes were founded too much upon conjecture ; it was 

 also much to be regretted that the whole matter had not been pre- 

 sented to the notice of scientific men in a fair and satisfactory form. 

 After a careful examin'ation of these authors, and with the view of 

 embodying much new and important matter from various scattered 

 memoirs and monographs, Mr. Reeve adopts the proposed system 

 of arrangement, considering it only a matter of surprise, that whilst 

 many eminent conchologists are indefatigable in describing new spe- 

 cies, a revision in the general distribution of these animals has been 

 so long neglected. The Lepades and MoUusca are to be considered 

 as separate and distinct sub-kingdoms. The Lepades are divided 

 into two orders, according to the established method, the sessile and 

 pedunculated ; and the Mollusca into five classes, upon the modifica- 

 tions of the organ of locomotion. The first class is divided, in imi- 

 tation of Lamarck, according to the number and position of the 

 adductor muscles, as indicated by the cicatrices or points of at- 

 tachment on the internal surface of the shell. The second class 

 includes but few species, and is distributed at once into families ; 

 the animals of this and the former class are all conchiferous, having 

 a bivalve shell ; the valves are connected by a ligament in the first 

 class, but not in the second ; their general organization too is es- 

 sentially diff'erent. The third class, which comprehends by far the 

 greater part of the Mollusca, is divided into seven orders, according 

 to the varieties of the structure and position of the branchiae, the 

 system of respiration being the most important feature of distinction 

 in the organization of these animals : this plan of subdividing them 

 was proposed by Cuvier, and has been for the most part followed by 

 subsequent naturalists. The animals of this class are not all con- 

 chiferous ; some are naked, or entirely destitute of shell, and do not 

 therefore come under the present notice. The fourth class contains 

 but few genera ; they include a singular kind of moUusk, having a 

 small glass-like shell, found swimming in myriads on the surface of 

 the ocean by means of a small wing-like natatory fin. The fifth and 

 last class, which contains the Nautili, are divided into two orders, 

 according to the plan of Lamarck. The following Table exhibits 

 the primary distribution of these animals, with their subdivision into 

 families ; added to which is the entire classification in detail : — 



