208 MESSRS. BRADY, PARKER, AND JONES 
the remainder would be sufficiently provided for by association with Polymorphina 
Thouini, P. fusiformis, and P. compressa. 
Whilst speaking of the literature of the genus, we may advert to the difficulty of iden- 
tifying the particular varieties figured by some of the earlier writers. The value of an 
otherwise excellent paper, like that by Herr Roemer on the North-German Tertiary 
Marine Sands, is much diminished, so far as the Foraminifera are concerned, by the 
minuteness and want of definition of the drawings; and the same fault appears in Prof. 
Reuss's earlier illustrations. The desire to express relative size, by observing a uniform 
scale for all the figures on a plate, has in the same way somewhat marred the usefulness 
of our own Monograph of the Crag Foraminifera; but in this case the deficiency is con- 
fined to the smaller species. 
. A treatise on any subject pertaining to fossil microzoa can hardly be regarded as com- 
plete without reference the * MIKROGEOLOGIE ” of Prof. Ehrenberg, although so far as 
the “ Polythalamia”” are concerned, the value of its magnificent plates is very small in 
proportion to the labour bestowed upon them. Their defects are chiefly due to the 
system adopted throughout the work of drawing from specimens mounted in Canada 
Balsam and viewed by transmitted light. The result is that only one aspect of the test 
is given, and in transparent individuals the external characters are confused beyond re- 
cognition by the prominence of the septal lines in the interior. The figures, almost 
without exception, represent the longitudinal or horizontal section of the shell, from 
which, alone, the shape of its transverse section or its general external aspect cannot be 
determined. Under these conditions the compressed and complanate forms are undis- 
tinguishable from the subglobular and pyriform varieties, and the only characters left 
for diagnosis are the comparative length and breadth of the specimens and the contour 
of their margins. Whilst therefore we have thought it necessary to examine minutely 
all the figures in the * Mikrogeologie’ showing any apparent connexion with this 
genus, and have, to the best of our judgment, distributed the references to them amongst 
the synonyms appended to the species to which they seem to belong, the result is offered 
with much hesitation, and the determination must be accepted with a certain amount of 
reservation. The difficulty attending this re-setting of Prof. Ehrenberg's subdivisions 
is further enhanced by his non-acceptance of previously established and well known spe- 
cific and even generic terms. We find undoubted Polymorphinæ under no less than ten 
generic headings, intermixed with Foraminifera belonging to several widely differing 
types; indeed the nomenclature of the * Mikrogeologie' leaves us no terms of dis- 
tinction between such genera as Polymorphina, Textularia, Uvigerina, and Bulimina, 
whilst the subgeneric names Guttulina, Bigenerina, and Dimorphina are applied to spe- 
cimens that have no divisional characters in common with those for which they are 
pans by other writers. 
It seems necessary to make a passing allusion to the last memoir on our bibliographie 
list, Herr von Schlicht's work on the * Foraminifera of the Septaria-clay of Pietzpuhl,' 
which eame into our hands whilst engaged in revising the present paper. The institu- 
tion of two new genera (Atractolina and Rostrolina) for sets of specimens very slightly, if 
at all, divergent from previously well understood forms is a course which will scarcely 
