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 DIVISION II. NUMMUIACE/E. 



|. ;Nummula. Lam. Ca- 

 jierina. Brug. 

 Exterior form lenticu- 

 lar, without any apparent 

 opening; a spiral cavity 

 divided by septa into an 

 infinity of small chambers 



a. Perfectly discous. 

 PI. 1, fig 3,4. (2) 



GENERA. 



No siphon. 



Marine. 



Only one row of cham- 

 bers to each turn of the 

 spire. 



Fossil and living. 



b. (Siderolites, Lam.) The edge with blunt or 



sharp rays. PI. 1, fig. Z5. 



c. (Renulites, Lam.) Several rows of cham- 



bers to each turn of the 

 spire. 



Microscopic, 



2. Discob bites. (3) Lam. 



Spiral, all the turns vi- 

 sible and exposed. (4) PI. 



1, fig- 5 - 



No siphon. 



(1) The Nummulites are amongst the most widely-spread fossils, forming, al- 

 most exclusively, entire chains of calcareous hills and immense beds of building 

 stone. The Pierre de Laon is composed of Nummulites; the pyramids of Egypt 

 were constructed with stone of this nature, and are raised upon the rocks which 

 supplied it. They were formerly considered, by some, to be Lusus Naturae, by 

 which portions of calcareous matter assumed the form of organised bodies; by 

 others, as petrified seeds, opercula, bivalve shells, etc. etc. Breynius, in 1732, and 

 Gesner, in 1758, concluded them to be univalve shells, very analogous to the Am- 

 monites. Bruguiere thought that the animal was contained in the last chamber of 

 the shell. Cuvier considers them to be interior shells. To observe the chambers 

 more distinctly, let a drop of ink fall on the worn face, and when it is quite dry, 

 rub the Nummulite delicately on a stone to take off the exterior black, after which 

 all the points which have retained the ink become evident on a white ground, and 

 the interior organization is perfectly discovered. This practice is useful for recog- 

 nising several other delicate fossil shells. 



(2) These are the most common and the largest amongst the fossil species, but 

 the living species are very small. 



(3) The termination iles distinguishes the Genera exclusively fossil, no analogous 

 living species having been yet discovered. 



(4) This character distinguishes them from the S pirolinites , the absence of the 

 siphon from the Nautili. 



