ARTHEOPODA — CRUSTA CEA. 
95 
columns of scales, and Tuvrihims, witli from four to six 
columns. In the Jurassic Archacolcpas and the Cretaceous 
Loricula (Fig. 46, 6‘) the plates of the capitulum are dis- 
tinguishable, but are not so fully developed as in Pollicipes 
and Scalpdlum, which, first found in Jurassic and Lower 
Cretaceous rocks respectively, continue to our own day. Tlie 
riiocene Crags of East Anglia furnish many Balanidae, 
essentially a Tertiary family, though some Devonian fossils 
from North America have been referred to it. 
The rest of die fossil Crustacea belong to the Sub-Class 
MALACOSTRACA (soft shells), an old name originally 
intended to distinguish these “ shell-fish ” from those with 
liard calcareous shells. There are nineteen (or twenty) body- 
segments, of which eight form tlie thorax, and six (or seven) 
form the abdomen. ]\Iost of the larger and better known modern 
Crustacea fall within this Sub-Class. Into the unsettled 
(question of their classification we shall not here enter, but 
merely allude to those (Drders or other groups that are 
represented by fossils. First comes the group Phyllocarida, 
in which are doubtfully but conveniently placed a number 
of I’alaeozoic Crustacea, which may or may not be related 
to the recent Nehalia. These have over the head and thorax 
a large shield, which may be folded as in the Phyllopoda, 
and may bear a narrow beak-like plate loosely joined to 
it in front. The abdomen consists of ring-like segments 
(seven in modern forms), and the telson has side-spines. In 
Hymcmcaris, from the Cambrian rocks of Wales, the sliield 
is in one piece. In Caryocaris from the same rocks it is 
l)ivalve, as also in the Ordovician and Silurian Geratiocaris, 
which was .sometimes two feet long, and in the Devonian 
genera, Eckvmcans from North America and Aristozoe from 
Bohemia. In Bhinocaris, from the Devonian of New York, 
a third plate arose in the middle of the back between the 
two valves. Discinocaris and allied forms, ranging from 
Ordovician to Trias, had an almost circular divided shield, 
much like the brachiopod shell Discina, while Aptychoj)sis 
and others have been confused with the similarly shaped 
opercula of ammonites (compare Fig. 83). 
There have long been known from Carboniferous and 
Permian rocks some genera differing greatly from their 
contemporaries and placed in a division Syncarida. These 
are now considered to resemble and to be related to a 
remarkable Crustacean called Anaspides, whicli lives in 
fresh-water pools near the top of Mt. Wellington, Tasmania. 
Gallei’y 
VIII. 
Table-case 
22 . 
Wall-case 
13 B, C. 
Table-case] 
22 . 
Wall-easel 
13b. 
