92 Canon A. M. Norman — Kotes on the 



such a species as nitida tliis hollow or lumen is very manifest ; 

 but in most cases the lumen is only indicated by a line seen 

 along the centre of the bar, which, whether actually visible or 

 not, may be called the lumen-line. On this lumen-line there 

 are often openings into the lumen, which may be called 

 lumen-pores (see woodcut, line of C), at other times calcareous 

 matter is heaped up along the lumen-line, so that a strong rib 

 is formed. The side of the bar may be called the lateral 

 line, and the poral openings usually developed upon it may 

 be styled lateral lacunes*, and those at its extremity median 

 lacunes. 



The great peculiarity in the structure of this group consists 

 in the curious fact that, while the openings along the centre 

 of the bars are simple pores or openings into the lumen, no 

 lacune, whether lateral or distal, is ever formed without the 

 combined assistance of two adjacent hars ; and indeed in the 

 posterior portion of such a species as GattycE, where several 

 bars meet at one point, at that point three, or even four, bars 

 seem sometimes to contribute to the building up of the circle 

 of a single very small lacune. In the woodcut the semicir- 

 cular hollows which break the lateral lines indicate the portion 

 of as many lacunes which that line contributes to form, and 

 similarly the two distal hollows indicate the share which this 

 bar takes towards the structure of two of the median lacunes, 

 the remaining portion of which will be supplied by a bar or 

 bars which have their origin in the opposite wall of the 

 zooecium. A lateral lacune therefore consists of two parts 

 divided horizontally (see E), owing its origin to the lateral 

 walls of two adjacent bars ; while a median lacune consists 

 of two vertical portions contributed by the distal extremities 

 of two opposite bars F. 



The Cribrilinidan zooecia which are figured and described 

 here were thus treated : — After being boiled in liquor potassse 

 they were again boiled in water, the water poured off, and 

 the shell or stone dropped into cold water, when the zoarium 

 often at once detaches itself; and if it should not a slight 

 pressure with a scalpel at its edge will often suffice to dislodge 

 it. If this does not succeed the shell is held against the side 

 of the flame of a spirit-lamp in such a way that the surface 

 opposite to that to which the zoariu^i is attached is in contact 

 with the flame, and the shell, when it is extremr-ly heated, is 

 suddenly dropped into cold water, when the zoarium is usually 

 liberated ; in obstinate cases the heating has to be repeated. 



1 undertook the following investigations from the desire 



* Lacuna, a space not filled up. 



