73 
themselves to the subject. In illustration of the progress of Con- 
chology, 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 
Synopsis. 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 with 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 examination of these authors, and with the view of 
embodying much new and important matter from various scattered 
memoirs and monographs, Mr. Reeve proposes the foregoing 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 Mollusca 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 different. 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 branchiz, 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 mollusk, 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 :— 
