CARBONIFEROUS BRACHIOPODA. 
271 
had been polished. The acid used is that which is usually supplied at the chemists, and 
the strength of it is not so material as its careful use.^ 
1 have devoted two entire plates (Sup., Pis. XXXI and XXXII) to give correct and 
unrestored drawings of some of Mr. Glass's admirably developed specimens, and will 
hereafter add another plate containing many equally beautiful and similarly worked-out 
Silurian specimens ; but let it not be supposed for an instant that, in order to obtain 
such valuable results, very many failures and the sacrifice of a large number of spe- 
cimens are not entailed. In many cases, of course, Mr. Glass has failed to find a sparry 
matrix, and even where this was found, in many instances the spirals were totally absent, 
or only one of the spires existed ; while in others the spires had got broken from their 
attachment to the hinge-plate, and had been displaced in the interior of the shell previous 
to the introduction of the soft liquid substance, which originally composed the matrix (see 
Sup., PI. XXXI, figs. 1 to 3, PI. XXXII, figs. 1 to 20, and PI. XXXIV, fig. 1). We 
need not, however, feel surprised at the spiral appendages being found so often wanting, 
or broken, or displaced in so many specimens, for how often do we find in dead specimens 
lying at the bottom of the ocean the loop of Waldhemia broken, prior to having been 
filled with the liquid mud which afterwards hardens into stone. 
In a small proportion only of the specimens did the spirals occur perfect and in 
their natural position. Mr. Glass was in many instances able to expose the spiral coils 
from the dorsal, ventral, and frontal aspects, and even to detach them entire from the 
interior of the shell, so that they could be studied completely.^ 
Mr. Glass was also able to detect and determine the exact space occupied by the 
spirals in the interior of the shell, as well as their direction, and to show that, for 
instance, in the case of Spirifera glabra, the spirals occupied as much space in the 
interior of the shell as in other species of Spirifers, consequently that the so-termed genus 
Martinia of M'Coy, founded on the supposed existence of very small spiral appendages, 
can not be substantiated, and being established on a palpable error must consequently 
be erased. Mr. Glass has also observed, as I had done previously, that very often a 
Spirifer is not equilateral, for in many cases one wing or lateral half of the shell is shorter 
than the other, and that this efiects likewise the length of the spiral coils and the 
^ Mr. James Neilson, jun., has likewise been successful in developing the spirals in Athyris Royssii 
(Sup., PI. XXXIV, fig. 7) and Spirif. lineata. He operated in a somewhat similar manner as the 
Rev. N. Glass, making use of diluted hydrochloric acid aided with a file and knife ; and if the shell 
is to be preserved it may be coated with wax or paraffin. The specimens of Athyris Royssii and 
Sp. lineata, found at Dockra and other places close to Beith, in Ayrshire, generally contain the spirals 
undisturbed, but the specimens do not come as sharply worked-out as Mr. Glass's, and this is due to 
the difl'erence in the nature of the matrix. 
2 My sincere and grateful thanks are due to several friends who kindly assisted the Rev. Norman Glass 
to procure suitable specimens for his operations. Among these we may name Mr. HoUier, of Dudley ; 
Prof. T. McKenny Hughes, of Cambridge ; Prof. Dawkins, of Owen's College, Manchester ; Mr. J. Plant, 
of Peel Park Museum, Salford ; and Mr. J. Tym, of Castleton, Derbyshire. 
