DEPARTMENT OF GEOLOGY 
23 
the animal to which they belonged must have stood higher at the 
shoulders than at the hips. 
Halls 36, 59, 60, and 61. 
These halls are devoted to fossils of the remaining geological 
periods, from the Jurassic onward. Owing to the size of many 
of the specimens it has not been possible to place them in exact 
geological order, but groups are shown together as far as possi- 
ble. 
Jurassic Period. — Goniospongia, Cnemidiastrum, Retispongia, 
Craticularia, Hyalotragos and Pyrgochonia illustrate the various 
forms of Jurassic sponges. Rhizostomites shows the form of the 
gastral cavity of a jelly-fish. 
Two types of Crinoids are shown. The first, illustrated by 
Pentacrinus, had a comparatively small body attached by a 
a long stem and a large number of long, many-branching arms. 
The other type, illustrated by Antedon, was a stemless, free- 
swimming form with only a few short arms. 
Ophiura and Asterias are typical starfishes. 
Jurassic Sea-urchins are of two types and a representative 
series of each is shown. Cidaris, Hemicidaris, Acrocidaris, Dia- 
dema, and Stomechinus belong to the type having the shell di- 
vided into five equal rays. Echinobrissus, Pygaster, Hyhocly- 
peus, and Clypeus represent the other type, in which the sym- 
metry^ is bilateral instead of radial. 
Many species of Brachiopods are shown but the majority of 
them belong to the genera Terebratula and Rhynchonella. 
Molluscs were the most characteristic group of invertebrate 
animals in Jurassic time and both the Pelecypods and Gastro- 
pods bore marked resemblance to modem forms. Among Pele- 
cypods are shown Oysters such as Ostrea and Gryphcea] Scol- 
lops such as Pecten, Li^na, and Avicula; and Mussels and Clams 
such as Modiola, Pinna, Pleuromya, Pholedomya, Trigonia and 
Cardina. Diceras is a shell in which the beaks of each valve are 
long and coiled like a horn. Nerinea, Natica, Pleurotomaria, 
Cerithium, Turbo, and Trochus represent the Gastropods of this 
period. 
Three distinct types of Cephalopods are shown. The first 
is illustrated by Nautilus, with a series showing variations in size 
and ornamentation. Polished sections show the internal char- 
acters of the shell. 
