394 Mr. A. H. Foord on '' Ortlioceras 



chambered testaceous animal which I hare seen alive or 

 dead. Its form is rather cylindrical than conical, and im 

 addition to its great breadth it has a length of six feet and 

 more, so that we are convinced that it surpasses in magnitude 

 all Ammonites hitherto discovered, and that it is thus the- 

 largest of all univalved testaceous animals. Its siphnncle is 

 mostly situated quite on the margin or on the circumference 

 of the shell, and not quite hidden by the joints of the external 

 shell ; occupying about a third part of the entire shell. On 

 account of its situation on the margin, the segmental par- 

 titions [septa] of the shell form very oblique rings on the 

 surface of the siphuncle, and at the same time run outwards 

 over its face, whence it results that the siphuncle seems as it 

 were to consist of hoods or wrappers, set or inserted upon one- 

 another, as if it sent out processes. The outer wall of the- 

 siphuncle is entire and free from perforations, showing no 

 point of communication between the cavity of the siphuncle- 

 and the chambers of the exterior shell." 



The author then proceeds to describe the smaller Orthoeeras^ 

 lodged in the siphuncle of " Orthocero.s duplex^'' from whicb 

 circumstance the specific name originated. It need hardly be 

 said that the included Orthoceras was introduced by accident 

 into the capacious siphuncle of the larger one *. Judging" 

 by Wahlenberg's description, which is almost confirmed by 

 his reference to one of Klein's figures (' De&criptiones Tubu- 

 lorum Marinorum,' 1731, tab. vi. figs. 1, 2), his species waa 

 most probably Endoceras trochleare. 



It appears that Wahlenberg's views regarding the im- 

 prisoned specimen were not shared in by some of his scientific 

 brethren, for he observes with much naivete that " many 

 people interested in natural phenomena have regarded this 

 internal Orthoceratites as a different species, on account of its 

 annular form ; and the inhabitants of Mount Kinnekulle well 

 distinguish it from the common Orthoceratites under the name 

 " Svecico skrufstenar" [Swedish screw-stone], a by no means, 

 inapt sobriquet for Endoceras trochleare. 



Selecting from Wahlenberg's description of ^^ Orthoceras 

 duplex " those parts of it which are essential to a specific 

 diagnosis, they are found to consist of two only, viz. the form 

 of the shell, which is said to be "rather cylindrical than 



* This is of course uo uncommon thing. Barrande gives numerous 

 figures of Endoceras and Ortlioceras into -whose siphuncles young or 

 smaller shells belonging to those genera have been introduced after the 

 de"ath of the animal and the partial destruction of its shell. (See Syst. 

 Sil. de la Boheme, vol. ii. pi. ccccxxxviii. figs. 9, 11 ; also Pal. of New 

 York,.by James Hall, vol. i. 1847, pi. xlviii. fig. 3.) 



