Alonthly MicroscopiCiil"! 
Journal, iMay 1, 1869. J 
Parkeria and Loftusia. 
299 
ing ; it must therefore be heated in an iron pot, and dihgently 
stirred till the mass acquires a purple colour ; it is then of the 
requisite degree of hardness. Both this and the putty-powder 
must be washed to separate gritty particles ; about five minutes 
will be sufficient. After obtaining all that can be suspended in this 
time, the residue may be levigated on an iron plate with a soft iron 
spatula, and the washing continued at pleasure ; but the result of 
all the washings is sure to contain some gritty particles, which 
must be separated by repeated washings, till nothing whatever will 
settle at the end of five minutes. Two sizes of crocus only are 
needed ; the last is obtained from the washed mass after one hour's 
suspension, and is very small in quantity, but of much value for 
obtaining the finest polish on prism work, either in glass or calc 
spar. The ordinary washed crocus, used alone, I have found too 
keen, and apt to cling to and raise streaks on the polishing laps ; I 
therefore always mix it with an equal part of the putty-powder, 
which quite remedies the evil ; an uniform mixture is best obtained 
by stirring them together with water. 
(To he continued.') 
YI. — Description of Parkeria and Loftusia, two Gigantic Types 
of Arenaceous Foraminifera. By Dr. Carpenter, Y.P.K.S., 
and H. B. Brady, F.L.S.* 
The authors of this memoir commence by referring to the separa- 
tion of the series of Arenaceous Foraminifera from the Imperforate 
or Porcellanous, and from the Tubular or Vitreous, first distinctly 
propounded in Dr. Carpenter's ' Introduction to the Study of the 
Foraminifera ' (1862), on the basis of the special researches of 
Messrs. Parker and Kupert Jones ; who had pointed out that, whilst 
there are several genera in some forms of which a cementation of 
sand-grains into the substance of the calcareous shell is a common 
occurrence, there are certain genera in which a " test " formed entirely 
of an aggregation of sand-grains takes the place of a calcareous 
shell ; and that these genera constitute a distinct family, to which 
important additions might probably be made by further research. 
The propriety of this separation of the Arenacea from the 
calcareous-shelled Foraminifera has been fully recognized by Pro- 
fessor Eeuss, the highest continental authority upon the group ; 
who had come to accept the principle laid down in Dr. Carpenter's 
successive Memoirs,! that the texture ^f the shell is a ( haracter of 
* Dr. Shaipey has kindly permitted us 1o roproduce the follo\vin;^- abstract of 
this most important paper, 
t ' Pliil. Trans.; 185(3-G0. 
VOL T. Y 
