Gallery 
VIII. 
Case A6. 
Case A5. 
Wall-case 
12a. 
Gallery 
VIII. 
West side 
and 
Gallery 
VII. 
122 GUIDE TO THE FOSSIL INVERTEBRATE ANIMALS. 
# 
Arctic Ocean was ]>robably cut off l)y a land barrier to the 
north, while there was free communication with the seas to 
the south. The Museum possesses the specimens used by 
Busk in writing his monograjdi on the “ Crag Polyzoa,” and 
many of them are exhibited. The most interesting forms 
found in the Crag are some massive Cyclostomes, including 
the three species known as Alvcolaria semiovata, Fascicularia 
auranlmm, and F. hibipora. Among the Cheilostomes, the 
most remarkable forms are two species of Cellana \Sali- 
cornaria] and one of J^rdiceHta. The numerous species of 
Sdiizoporclla, Miicrondla, and Membranipora are closely allied 
to or identical with living forms. 
A small collection of Pleistocene species from the Clyde 
and from Selsea Bill is sliown ; but all the.se species still 
live on the English coast. 
Tlie Bryozoa from foreign localities are not yet com- 
pletely arranged, and only a few representative species are 
exhihited. The lowest slope of the wall-case is devoted to 
the Palaeozoic faunas, chief of which are those from the 
Ordovician and Silurian rocks of North America. The 
Carhoniferous fauna of the same continent furnishes some 
remarkable forms, notably Ardiiracdes Worthcni, which is 
like a Fenesfdla twisted into a screw, and Evadmopora 
qidnqueradiata, another Cryptostome with a star-shaped 
colony. 
A collection from the Bathonian deposits of Northern 
France on the middle slope contains several interesting 
forms, notably Onydiocdla Jlahdliformis, which is the oldest 
true Cheilostome known. 
Among the Tertiary Bryozoa on the top slope, the large 
specimens from the IMiocene deposits of the Mediterranean 
are most worthy of notice. 
The Trustees have published a Catalogue of the Jurassic 
Bryozoa (1890), and the first two volumes of a Catalogue of 
the Cretaceous Bryozoa (1899, 1909), all by Dr. J. AV. Gregory. 
lAIOLLUSCA. 
The.se animals derive their name from their soft bodies 
{mollis, soft), which never have any internal skeleton, and 
rarely any hard appendages capable of preservation as fossils. 
The glandular skin, however, usually secretes, on a portion of 
the outer surface called the mantle, a hard shell, sometimes 
horny in appearance, but usually thickened by a deposit of 
