158 GUIDE TO THE FOSSIL INVERTEBEATE ANIMALS. 



Gallery 

 VII. 



Table- cases 



2&3. 

 Wall-cases 

 1, 2, 13 & 

 14. 



Wall-case 

 14. 



Wall-ease 

 1. 



nature to that of the other cephalopod shells. It is confined 

 to the female and is secreted mainly by her arms, with which 

 she enfolds her body. Their inner surfaces deposit this paper- 

 like shell, which serves as a protection for the brood. A few 

 examples have been found fossil. 



We pass now to the General Collection, which is divided 

 into the three Orders, Nautiloidea, Ammonoidea, and 

 Coleoidea or Belemnoidea, 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 which a list was published by the Trustees in 1898. 



Order. — NAUTILOIDEA. Among the uncoiled Palaeo- 

 zoic fossils placed in this Order, there are many which 

 increased knowledge will probably cause us to ally with the 

 Ammonoidea or with the Coleoidea. Endoceras and its 

 allies, for instance, are generally admitted to be among 

 these (Fig. 79). Many exhibited specimens come from 

 Sweden and the Baltic provinces, where they are common 



in a reddish-green lime- 

 stone, of Ordovician age, 

 which, owing to thin layers 

 of shale, splits readily into 

 flagstones. Thus fine speci- 

 mens may be seen in the 

 pavements of Swedish towns. 

 A fine example, showing the 

 extraordinary length of the 

 shell, is in a framed slab 

 on the wall by the door. 

 Adjoining Endoceras are the 

 obscure but deeply interest- 

 ing specimens of Piloceras 

 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 Adinoceras aud Huro- 

 nia. In Adinoceras (Fig. 88) 

 the visceral cone seems 

 to have been constricted 

 by the septa into a series of beadlike swellings. The wall 

 of these was stiffened, and as the siphuncle gradually shrank 



Fig. 88. — Adinoceras, the siphuncu 

 lar structures. A fragment of A 



Bigsbiji, 

 tinuous 

 beaded 

 through 

 siphon, 

 Foord.) 



(s) 

 of 



con- 

 the 



showing septa 

 with the wall 

 neck-tube ; /, openings 

 the latter to the endo- 

 Natural size. (From 



