10 FOSSIL MOLLUSCA OE THE CHALK. 



must be due to decay. Geinitz has figured the lower portion of the Phragmacone, but his 

 figure is hardly intelHgible. 



Although the specimens of this Belemnite are found truncated at different attitudes, 

 and the fracture is either nearly flat or more or less conical, there are common characters 

 in the broken ends of all, which are without doubt connected with the manner of growth 

 of the shell. There are usually two more prominent ridges on each side, and three slighter 

 ridges on the back. The sides of the angular cone thus formed, appear to have some 

 analogy with the angular opening of B. quadrata, and render it probable that B. lanceolata 

 will be found to belong to the same division of the genus as that species. 



M. D'Orbigny has named this species B. vera, on the supposition that it is the 

 Actinocamax verus of Miller ; but the description given by that author proves that, as 

 Mr. Sowerby correctly observed in the ' Mineral Conchology,' A. verus is a worn specimen 

 of B. mucronata. Miller describes his species as having " two longitudinal, towards the 

 apex branching, impressions of blood-vessels." He also states that it is often found in 

 flints. Both the description and the placing in it in the chalk with flints are decisive 

 against regarding it as B. lanceolata. Every species of Belemnite, when rolled and worn 

 at the top, may present a form similar to that of Miller's figure 17 ; and the B. mucronata 

 especially, in decaying peels off in concentric layers, as in his figures 11, 12, and 18, 

 ' Geological Transactions,' 2d series, vol. ii, pi. 9. It is probable that when describing 

 Articonamax verus, Miller may have had before him worn specimens of several species of 

 Belemnite. Such names founded on misconception had better be allowed to drop. 

 But in this instance, as Miller's description applies to B. mucronata, there is no room for 

 his name of J. verus. The name first in point of priority is B. plenus of Blainville, which 

 has consequently been adopted. Sowerby's name, B. lanceolatus, is not only posterior to 

 Blainville, but had been previously applied by Schlotheim to another species. 



Length, 3^ inches ; greatest breadth, fths of an inch. 



Common throughout the grey chalk of the South of England, and found in the lower 

 beds of the chalk in Belgium, Germany, and the North of France. 



Nautilus, Linn. 



Shell discoidal, spiral, chambered, compressed or ventricose, with contiguous whorls 

 regularly convoluted on the same plane, the last partially or entirely concealing the previous 

 whorl ; chambers separated by transverse, concave septa, with simple sinuous margins, 

 and traversed near their centre by a continuous siphuncle ; the last chamber large, and 

 capable of containing the animal. 



