BRACHIOPODA. 
11/5 
exhibited series, and transferred, with all specimens of 
historical interest, to Gallery XI. An attempt was, there- 
fore, begun to show here specimens interesting from their 
habit or structure. Such are the examples of Spirifer, 
in which the arm-spires were worked out with a needle 
and acid by the Eev. Norm an Glass, and specimens of 
Tcrehratula and Ornithclla fiom the Cornbrash, showing 
the arm-loop. The interior of the shell is also well shown 
in a Liothyrina from the Norwich Chalk on the other side 
of the Case. Another Jurassic brachiopod Acantliothyris 
spinosa owes its name to the numerous spines borne by 
its shell ; these were very long and are generally broken 
off, but there are exhibited both British and foreign 
examples in which they are most Avonderfully preserved and 
displayed. Productus is another genus richly provided with 
spines, and these owing to their size are often found 
scattered in the rock as thin tubes ; a slab of Carboniferous 
Limestone covered with them is shown. A pretty impression 
in flint of the rare Trigonosemus elcgans is among the 
Cretaceous fossils. Various Jurassic Terebratulm and tere- 
In-atuloid shells reflect changes of growth, due to old age or 
illness, in variations of their ornament. The same outer 
form has frerjuently been assumed by brachiopods of different 
internal structure at widely separated geological periods, a 
circumstance very perplexing to the field-geologist ; but here 
is exhibited a set of four different species, belonging to at 
least three genera, all coming from the Inferior Oolite Marl, 
and so much alike that a casual observer could hardly tell 
them apart. A similar independent recurrence of form is 
displayed by Pyyopic and other “ diphyoid ” genera, in which 
the fore-part of the shell has grown out into two lobes that 
ultimately meet and enclose a vacant space. These various 
modes of growth and of evolution are by no means confined 
to Brachiopoda. They suggest that living creatures develop 
in definite directions, which are the consequences of some 
previous impulse or pi'evious conditions ; and that com- 
munity of a distant inheritance may lead to similar con- 
vergent results, especially when the outer stimulus is the 
same. 
Further information on the Brachiopoda may be sought 
in the memoirs by T. Davidson already referred to, and in 
“An Introduction to the Study of the Brachiopoda,” by 
J. Hall and J M. Clarke (Albany, 1904-5). 
Gallery 
VIII. 
Table-case 
17 . 
Table-case 
18 . 
Table-case 
17 . 
Wall-case 
llB. 
Table-case 
17 . 
Table-case 
18 . 
Wall-case 
llB. 
