100 (lUIDK TO THE FOSSIL INVERTEBRATE ANIMALS. 
Gallery 
VII. 
Wall-case 
1 . 
furins hiul a larger number of paired openings and could, 
^one siqiposes, stretch out more arms (Fig. 90). Ascoceras, 
■ which occurs in the Ordovician of Nortli America and the 
Silurian of Europe, especially Bohemia, had a curious life- 
history. This may be Ibllowed in the enlarged and dia- 
granimatically coloured model which is exhibited. Beginniruf 
with a narrow tubular shell, divided by transverse septa, and 
having a simple siphuncle near the margin (Fig. 91 it 
suddenly swelled out like a J'ntcrioco’fifi. d'his gave moi'e 
Fig. 91. — Ascocoraticlm. A, upper part of shell of Ascoccras munubrium, 
cut down the middle, showing the upward-curved septa on the left ; 
B, C, I), largo curved septa of Ascoccras fistula ; K, upper part of shell 
of Ascoccras decipiens, with septa of ordinary type formed after the 
deposition of the upward- curved septa ; F, the shell of the same species 
completed, showing the simple nautiloid portion (u ) ; 0, IT, fragments 
of an allied form, Choanoceras. (From Foord, after Lindstrom.) 
room for the visceral cone with its contained genital glands, 
and naturally changed the character of the septation (Fig. 91 
A, F). The body now liad so much room that it ceased to 
advance to any great extent. On the contrary, as the animal 
grew older its body contracted, and first the opening of 
the body-chamber narrowed somewhat. Then the visceral 
hump shrank a little at its end, but more at the side, much 
as it did in the early stages of Endoccras. Thus the septa 
now produced remained close together at the apex of the 
body-chamber, and the siphuncle between them was swollen 
