177 



it and figures it as a belemnite^ with a small circular hole at 

 the extremity of a curved point, and, beneath this part, a 

 narrow small opening. De Montfort speaks of its having 

 chambers and a central siphuncle, but does not state whether 

 these are formed in the spathose substance, or whether they 

 are of a shelly substance and fixed as an alveolus in the 

 spathose substance. 



Thalamus. — The fossil which is here referred to does 

 not appear to have a single pretension to be placed in a 

 distinct genus. The belemnites polymitus of Scheuchzer is 

 taken for its type, and the external markings which de- 

 signate its generic characters are thus accurately described 

 by Scheuchzer: — "Belemnites cujus superficies undique 

 circulis concentricis est obsita." — Lapid. figurat. Lub. p. 15. 

 Walch, who noticed the same markings, was of opinion that 

 they were merely accidental, and were probably produced 

 by the adhesion of flat spiral shells. But similar markings 

 are frequently found on the green-sand fossils. I have it 

 in several instances, and particularly on a belemnite, exactly 

 agreeing with the description of the belemnites polymitus of 

 Scheuchzer. These markings are formed of patches of 

 chalcedony, in rude sub-concentric forms, having somewhat 

 of a stalagmitic appearance : I have seen a mass of chal- 

 cedony, its surface thus covered, and its substance appa- 

 rently thus formed, from Devonshire, as large as a man's fist. 



Amimomus. — The fossil for which this genus is formed 

 is said to be figured in the Supplement to Knorr's work, 

 Tab. iv. fig. 2, but no such fossil appears in the place to 

 which we are referred. 



Tiranites — is the name of a genus under which it is pro- 

 posed to place a fossil described and figured by Knorr, Supp. 

 Tab. xii. fig. 1 to 5 ; and also found in the neighbourhood 

 of Rouen by M. de Montfort, who thus describes it : — " A 

 free, chambered, straight, tubular cone ; chambers undulated 



A a. 



