6 Prof. W. King on Spiriter cuspidatus. 
of colour. Very few of them present a definite form, their outer 
portion being generally irregular and lightest in colour, shading 
off into the subtranslucency of the surrounding fibres*. It 
is extremely rare to see the perforations pushing the fibres 
aside; the latter pursue their course, as 1t were, with very 
seldom any appearance of being forced either to the right or 
the left by the former. When the perforations are pale, it is 
only by their being slightly less translucent than the fibres 
that their presence can be with safety determined. Frequently 
there are breaks in the lines of perforations; and spaces, ap- 
pearing to be imperforate, lie next to others undoubtedly per- 
forated. In two of the sections no perforations are seen, 
except perhaps what might be considered to be, in two or 
three cases, the faintest traces of them. 
Whatever be the cause of the absence of the perforations in 
the preceding sections, the following additional points ought 
not to be overlooked in considering this question :—(1) The 
perforations often appear as if they stopped short of one of the 
surfaces of the sections. (2) The sections often exhibit what 
appear to be very minute perforations intermixed with the 
ordinary-sized ones. (3) I have occasionally seen two fibres 
appear as if crossing the transverse section of the perforations, 
where the latter are faint. These points, and the indefinite out- 
line of the perforations, the little or no deviation they produce 
in the ordinary course of the fibres, also their “ patchy distribu- 
tion” (in which the sections agree with those examined by 
Meek and Carpenter), certainly do not ordinarily prevail 
among perforated Palliobranchs, at least in recent species and 
others, occurring in Tertiary and Secondary rocks, which have 
undergone no metamorphism. 
It may now be mentioned that I“ suspected ” Spirifer cuspi- 
datusto be perforated, from “patches of faint, slightly raised, oval 
impressions’ being ‘ present on the subsurface shell-layers ” 
of Mr. Birmingham’s specimen—and that I expressed an opi- 
nion of the “‘impressions”’ being each caused by the rising- 
up of the fibres around a perforation, such as takes place in 
Waldheimia australis and other recent speciest. This rela- 
tionship between the impressions and the perforations is proved 
by the evidences illustrated in Pl. II. Fig. 4 represents the 
* According to one of Mr. Meek’s drawings, the perforations, as seen in 
a variety, or an allied species (Sp. swbeuspidatus), are distinctly defined— 
so much so that Mr. Meek informs me that he has “in some instances had 
under the microscope a single isolated fibre with half the diameter of a 
perforation cut out on one side (shown in PI. III. fig. 3), as illustrated by 
Carpenter in some of his publications.” 
+ Geological Magazine, June 1867. 
