56 
THE VOYAGE OF H.M.S. CHALLENGER. 
misleading ; therefore it is manifestly better to abandon an initial subdivision based 
solely on the condition of the investment with respect to perforation. 
The adoption of three Sub-orders, instead of two, depending on shell-texture rather 
than on mere perforation, as latterly proposed by Reuss, meets the difficulty in part, 
but is still open to objection. On the one band, there is a considerable group of true 
Miliolce, our knowledge of which is much extended by the Challenger collections, that have 
rough arenaceous tests ; and on the other, the large and important family Textularid^e 
is practically unprovided for, inasmuch as it is sometimes truly arenaceous, sometimes 
hyaline and perforate, and sometimes externally sandy but with an inner perforate shell. 
The author endeavours to meet this difficulty by dividing certain genera and placing the 
two halves in different Sub-orders ; thus Textularia appears as Textularia amongst the 
hyaline forms and as Plecanium amongst the arenaceous, and Bulimina in the same way 
as Bulimina and Ataxophragmium ; but this is cutting the knot rather than untying it, 
and even were so summary a method practically convenient, the proposal to split a 
natural group like that comprising the Textularian and Bulimine types in order to meet 
the exigencies of an artificial distinction, is not one to be lightly adopted. 
Passing from Sub-orders to Families, even greater anomalies are apparent, especially 
amongst the hyaline forms. For example, Spirillina is found at almost the opposite 
end of the scale to the Rotaline genera ; Nodosaria, Cristellaria and Polymorphina are 
placed in three different Families, whereas, in point of fact, they are connected by inter- 
mediate and dimorphous modifications, so as to form an absolutely continuous series ; 
and Textularia , Bulimina and Cassididina are similarly separated. These appear to me 
fatal objections to the details of the classification, viewed as a natural arrangement. 
What has been already urged against the employment of the terms Perforata and 
Imperforata in Reuss’s scheme, applies with equal force to that of Dr. Carpenter and 
his colleagues. There is, however, in the English arrangement but little infringement 
of natural relationship in the constitution of the Families, except, perhaps, the 
association of Textularia and its immediate allies with Globigerina and the Rotaline 
genera. Apart from this, its chief drawback is that the divisions are too large to 
be zoologically convenient, a defect more and more felt as the number of known genera 
is augmented. 
Rupert Jones, in his outline, entirely omits the forms having chitinous tests 
( Gromida ), and, following Reuss’s example, divides the Foraminifera into three Sub- 
orders, namely, Porcellana, Arenac ea, and H valina. He employs the term Imper- 
forata as a synonym for Porcellana, that is to say, for a section exactly coextensive 
with Carpenter’s family Miliolida; whilst Perforata is given as an alternative for 
Hyalina. In other respects the general plan differs from that of the “ Introduction,” 
chiefly in the redivision of the Sub-orders into a larger number of Families. 
Turning now to the synopsis in Professor Zittel’s Handbook of Palaeontology, we 
