6 AUSTRALASIAN ANTARCTIC EXPEDITION. 
PART I. 
SYSTEMATIC DESCRIPTION. 
PRELIMINARY REMARKS ON SPICULES AND SHELL STRUCTURE, 
Before discussing the species in detail, it is desirable to give an account of the 
calcareous spicules contained in the soft parts of certain brachiopods, since no good 
presentation of the existing state of knowledge as to these bodies has yet appeared in 
any English publication. 
The spicules generally consist of nearly flat plates of calcite, and each one is 
composed of a single crystal of the mineral, so oriented that the plane of flattening is 
parallel to the basal plane (111).. The plates therefore give good uniaxial interference 
figures in convergent polarised light. They are frequently perforated by a number of 
holes, which I have termed “ windows,” and generally give off a number of angular 
lateral processes, so that some are almost stellate in form. The upper and lower surfaces 
of the plates are not infrequently adorned with numerous small spines. In other cases 
the spicules form linear, rod-like bodies, of less regular crystallog ‘aphic orientiation. 
In such species as bear them the spicules may be found in the body walls, the 
mantles or only the sinuses thereof, around the mouth, in the walls of the arms and in 
the cirri of the arms. They lie, according to van Bemmelen (1882) below the epithelium 
in the connective tissue, and are surrounded each by a membrane, of which they are 
the product. The genera in which they are known are Thecidea, Liothyrina, Liothyrella, 
Terebratulina, Chlidonophora, Eucalathis, Dyscol ia, Argyrotheca,* Platidia, Kraussina, 
Megerlina, Miihlfeldtia and Laqueus. 
The functions of the spicules are not yet well known. Occasionally adjacent 
spicules are united by their lateral process, and they may thus serve to act as an internal 
skeleton and strengthen the parts of the animal in which they lie. Deslongchamps 
(1884, p. 206) states that in Avaussina rubra the mantle is furnished with very smal] 
and thin spicules which serve to protect the circulatory organs, there being one system 
for the venous sinuses and another of different shape for the arterial organs. It may 
be supposed that in the short looped forms (Terebratulida) the presence of spicules in 
the free arms tends to give rigidity to these organs, which are unsupported by a 
calcareous loop.t The spicules are, however, relatively much more massive in the arms 
of the smaller species than in those of the larger, and if they performed a useful function 
of such a nature, it is difficult to see why they should not be found better developed in 
the larger species. 
Deslongchamps (1860, 1865, and 1884) was the first to make a study of 
brachiopod spicules and to employ them in classification. In 1884 he divided the 
Terebratulidae into two groups, the first, which included Liothyris (now Lnothyrina), 
* Blochmann does not recognise this genus as possessing spicules, but Dall (1871, p. 24) mentions that a few wer 
observed in the pallial sinuses of Cistella lutea=Argyrotheca, “t ) at a few were 
+ Twelvetrees and Petterd (1900) consider that this is the function of the spicules of i eneriina laftarekions 
