BRACHIOPODA. 
Ill 
called the “ lopliophore ” (tuft-bearer), and resembles the (^iiery 
structure of the same name in the Jlryozoa (Diagram 8). -^all-case 
The lopliophore is generally produced into two so-called n. 
‘•'arms,” which fill the forepart and sides of the shell-cavity 
and are often spirally coiled. Since they were formerly 
supjjosed to represent the “foot” of the Mollusca, their 
presence suggested the name Brachiopoda (arm-feet). The 
mouth leads to a slightly coiled intestine (Diagram 1 0), which 
in the simpler genera is provided with an anus, whence the 
Class comprising them received the name Tretenterata 
(pierced guts). Fos.sils indicate that some of the earlier 
genera of the other Class were also provided with an anus ; 
but in its later genera this structure became degenerate, and 
no longer exists in the living representatives ; for this 
Class, therefore, the name Clistenterata (closed guts) was 
proposed. These names are now generally supplanted by 
Inarticulata and Articulata (see p. 112). 
The Brachiopoda are found in seas all over the world, 
and usually at depths of less than 100 fathoms, but they 
have been dredged at a depth of 2,900 fathoms. Most kinds 
attach them.selves permanently to a hard bottom by the 
peduncle, open their shell so far as the hinge permits, and 
collect minute food-particles in the currents of water that 
flow down the lopliophore ; some protrude and even unroll 
the arms. Ling%da, as shown in Diagram 2, lives in a tube -wall-case 
in the sand, forming a case of agglutinated sand round the lOc. 
lower end of its peduncle ; it stretches its shell to the opening 
of the tube, and the projecting setaj guide the currents of 
water down to the lophophore ; but when disturbed, the 
peduncle contracts and the shell is withdrawn into the tube, 
which closes in above. It is not, however, to be inferred 
that all extinct species of Lingula and of similar genera 
lived in this way. 
Though brachiopods usually occur in great numbers 
wherever found, they are not so numerous now as they were 
in past ages. In the Carboniferous Epoch especially, the 
number of species and individuals was very great, and the wall-case 
Vroducti then living reached a larger size than any brachiopod 10. 
before or since. Terehratida grandis, of the Coralline Crag, Table-case 
is the largest brachiopod found in later rocks. Many 
examples of masses of brachiopod shells are exhibited, and 
among them may be mentioned a slab covered w’ith Lingu- Wall-case 
lella Davisi, from the Lower Lingula Flags of Upper Cam- 
brian Age, near Tremadoc; Ungulite Grit with Obolus and iob. 
