334 
REVIEWS. 
The surface of the shell in all Foraminifera is either smooth or 
diversified by some external sculpture, of those “ there are two prin- 
“ cipal kinds, which are for the most part related to the ‘ porcellanous’ 
“ and the ‘ hyaline’ types of shell-structure respectively.” In the 
porcellanous types the surface-marking is prone to take the form of 
pits or strise. “ Among the ‘ hyaline’ shells, on the other hand, 
“ variety is given to the surface-marking chiefly by the interposition 
“ of bands or spots of non-tubular substance in the midst of the 
“ tubular; such portions being distinguished by their vitreous lustre 
“ from the general surface, even when they do not project above it. 
“ Most commonly, however, they are raised into ridges or tubercles; 
“ and these are sometimes arranged with great regularity, whilst in 
“ other instances they are extremely variable.” 
Finally, as to the variations in size which the Foraminifera pre¬ 
sent, a few words may be said. Among the smallest forms may be 
mentioned the naked Lieberkiihnia , the diameter of which is about 
l-400th of an inch, and Squamulina , whose single-chambered shell is 
l-300th of an inch in its greatest length. Ovulites “ is the largest of 
“ the monothalamous Foraminifera; its one segment, which is 
“ usually about the size of a mustard seed, equalling in bulk the 
“ entire polythalamons shells of ordinary Miliolce, Fotalice , &c.” 
Fullenia , a very small polytlialamian has a “ diameter averaging 
“ l-50th and never exceeding l-30th of an inch.” But on the whole 
the Polythalamia far exceed the Monothalamia in size. The most 
notable Foraminifera in this respect are also the most highly 
organized, and belong to the family of Nummulinidce. The disc of 
Cycloclypeus measures 2 \ inches in diameter, while that of Nummu- 
lites itself varies from l-16th of an inch to inches. Next to 
Cyclolypeus the -complex type of Orbitolites is the largest of all the 
recent Foraminifera. 
The two principal features of Dr. Carpenter’s monograph will be 
found to consist—first, in the lengthened account which it contains 
of the structure of each particular type belonging to the Foraminifera; 
and, secondly, in the general classification of these animals, wherein, 
so to speak, the anatomical facts thus detailed are systematically 
summed up. It is true that, in his ‘ ‘ Researches on the Foraminifera,’ ’ 
he had already explained the organization of twelve of the most 
remarkable types belonging to this Order. Not only, however, are 
the results of these memoirs now again set forth, subject to such 
revision as seemed needful, but a large number of generic forms are 
here described, our previous knowledge of which had hitherto, with 
few exceptions, been most incomplete and unsatisfactory. Although 
the author’s peculiar method of investigating these types, by the 
careful comparison of thin sections of their shells made in different 
directions, had enabled him, in most cases, to arrive at tolerably 
complete conceptions of their conformation, he has, nevertheless, 
gladly welcomed the additional light which later opportunities of 
