158 GUIDE TO THE FOSSIL INVERTEBEATE ANIMALS. 
Gallery 
VII. 
Table-cases 
2 & 3. 
Wall-cases 
1, 2, 13 & 
14. 
Wall-case 
14. 
Wall-case 
1 . 
iiiiLurc to lliat oi' the otliev cepluilopod shells. It is confuied 
to the i'eniiile and is secreted maiidy by her arms, with which 
she enlolds her body. Their inner surfaces deposit this ])aper- 
like .shell, which serves as a ju’otection for the brood. A few 
e.xaniples have been found fos.sil. 
IVe pass now to the General Collection, which is divided 
into the three Orders, Nautiloidea, Ammonoidea, and 
Coleoidea or. lleleniuoidea, the smaller specimens as a rule 
being in the Table-cases and the larger ones in the Wall- 
cases. The collection is rich in types and figured specimens, 
of w'hich a list was publi.shed by the Trustees in 1898. 
Order. — NAUTILOIDEA. Among the uncoiled Paleo- 
zoic fossils placed in this Order, there are many which 
increased knowledge will probably cause us to ally with the 
Ammonoidea or wdth the Coleoitlea. Endoccrus and its 
allies, for instance, are generally admitted to be among 
these (Fig. 79). Many e.xhibited specimens come from 
Sweden and the Baltic provinces, wdiere they are common 
in a reddish-green lime- 
stone, of Ordovician age, 
W’hich, owing to thin layers 
of shale, splits readily into 
flagstones. Thus fine speci- 
mens may be seen in the 
pavementsof Swedish towns. 
A fine example, showing the 
e.xtraordinary length of the 
shell, is in a framed slab 
on the wall by the door. 
Adjoining Endoccras are the 
obscure but deeply interest- 
ing specimens of Pilocevas 
from the Durness Lime- 
stone of Sutherland and Tre- 
madocian beds of Canada 
(Fig. 80 a). Other genera of 
which the truly Nautiloid 
character may be questioned 
are Actinoceras and Huro- 
nia. In Actinoceras (Fig. 88) 
the visceral cone seems 
to have been constricted 
by the septa into a series of beadlike sw’ellings. The wall 
of these was stiffened, and as the siphuncle gradually shrank 
Fig. 88. — Actinoceras, the siphuncu- 
lar structures. A fragment of A. 
Bigsbyi, showing septa (s) con- 
tinuous witli the wall of the 
beaded neck-tube ; /, openings 
through the latter to the endo- 
siphon. Natural size. (From 
Foord.) 
