EEAUING SAS OMG Ne 
REVIEW OF SCIENCE AND INDUSTRY. 
A MONTHLY RECORD OF PROGRESS IN 
SCIENCE, MECHANIC ARTS AND LITERATURE. 
WO Se AUGUST, 1880. NO. 4. 
GZ OMOEA TIN IB) IMMUN GER VSILIONG Ve 
GEOLOGY AND EVOLUTION. 
BY THE LATE PROF. B. F. MUDGEE. 
CHAPTER I11.—MOLLUSKS. 
In the examination of the sub-kingdom of Mollusks, we find at the begin- 
ning nearly all ranks of groups fully represented. In the address of Vice-Presi- 
dent J. W. Dawson, before the American Association, in 1875, hesays: ‘‘Here then 
_ meets us at the outset the fact that in as far as the groups of annulose and mol- 
 luscous animals are concerned, we can trace these back no farther than in a period 
in which they appear already very highly advanced, much specialized and repre- 
sented by many diverse forms.” Development or evolution, if a law of nature, 
should begin with the lowest of each sub-kingdom, and symmetrically advance 
to the highest. But the first Mollusks of even below the Silurian, are associated 
_ with Pteropods, which are (next to the Cephalopods) the highest order; and the 
4 
latter soon appear. In addition, some of the lowest forms are late in coming 
forward on the stage of life. Some genera come and retire in a short period of 
time; others, like the Lingula, are seen early in the Lower Silurian, both in 
_ Europe and America, and are in existence in our present seas. 
The most noticeable feature of this question of development is, that in 
_ nearly all cases where a definite progression is claimed, either in this sub-king- 
_ dom or any other, the species are represented by few specimens. Where numer- 
= 6 ee 
ous fossils of one species are found, either no evolution is seen, or the progress 
IV—13 
