276 OBSERVATIONS ON THE ANIMALS 
latter—the siphuncle—is often undefended, being almost always 
placed at the extreme dorsal edge of the shell, and sometimes actu- 
ally outside it. 
Lastly, with regard to the distribution of the remaining groups of 
this genus, it is important to observe that the period throughout the 
formation of the oolites was by far the most abundant, in every 
way, in species, as well as individuals. Even in the limited state 
of our knowledge of the animal kingdom at that time, we can speak 
to not less than a hundred and fifty distinct species, every one cre- 
ated, living its appointed time, and becoming extinct, between the 
commencement and close of that series of limestone deposits. 
In all parts of the continent of Europe, as well as in Great Bri- 
tain, the fossils of this genus are extraordinarily abundant ; but they 
are not confined to Europe. Specimens have been found very high 
up on the Himalaya mountains, in Asia. They occur in the state 
of New Jersey, and in several other places in North America ; in 
Brazil, and on the coast of Chili in South America: and probably, 
when future researches shall have laid open the scientific stores of 
Africa and Australia, other species will there be found, showing the 
genus to have been once as widely distributed as it was undoubtedly 
locally abundant. 
It is rather singular that out of a number of allied genera, forming 
together an important natural family, one genus should be among 
the most widely spread of any that is known, and all the others 
- comparatively very rare, and occupying no important place in the 
scale of nature. Yet so it isin the case before us ; for the Ammo- 
nites are not more remarkable for their singular variety and great 
numbers, than the several genera, closely allied in every thing but 
external form, are for the very narrow limits within which they 
are confined. ‘The Hamites, next in order to the Ammonites, are 
not, indeed, quite so rare as the Scaphites or Turrilites already de- 
scribed ; but still they are only met with in a few strata, and in but 
one of those are they at all abundant. Of the different species 
known, two occur in the continental beds of the oolites; one 
so low down as the lias, while there are nearly thirty in the creta- 
ceous group, most of them occurring in the two beds of green sand. 
Of the Baculites, which come next, five species only are named at 
present, and all appear to have lived during the deposition of the 
chalk. The difference between these two last genera consists, to all 
appearance, in a very unimportant change of form, the Hamite 
being, as we have already observed, bent round more or less at the 
smaller extremity ov apex of the long, narrow, and often elliptical 
