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BRITISH BELEMNITES. 



Belemnites. 



Phragmocone horny, slightly nacreous, with a minute globular nucleus at the 

 apex ; divided internally by numerous concave septa. Pen represented by two 

 nacreous bands on the dorsal side of the phragmocone, and produced beyond 

 its rim in the form of sword-shaped processes. Guard fibrous, often 

 elongated and cylindrical, becoming very thin in front where it covers the 

 phragmocone. 



Section I. — Acceli, Bronn. 



Without dorsal or ventral grooves. 



Subsection 1. — Acuarii. 



Without lateral furrows, but often channelled at the extreme 

 point. (Example — B. acuarius. Lias. 



Subsection 2. — Clavati. 



With lateral furrows. (Example— B. clavatus. Lias.) 



Section II. — Gastrocceli, D' Orb. 



Ventral groove distinct. 



Subsection 1. — Canaliculati : no lateral furrows. (Example — B. canuliculatus. 

 Inf. Oolite.) 



Subsection 2. — Hastati : lateral furrows distinct. (Example — B. hastatus. 

 Oolite.) 1 



Section III— Notocceli, D' Orb. 



With a dorsal groove, and furrowed on each side. (Example — B. 

 dilatatus. Neocomian.) 



Belemnitella, J)' Orb. 



The guard has a straight fissure on the ventral side of its alveolar border; its 

 surface exhibits distinct vascular impressions. The phragmocone is never 

 preserved, but casts of the alveolus show that it was chambered, that it had a 

 single dorsal ridge, a ventral process passing into the fissure of the guard, and 

 an apical nucleus. (Example — B. mucronatus. Chalk.) 



1 Blainville, by whom the species was named, quotes it as from Lias, and also from the Clay of the 

 Vaches Noires (Oxfordian). It seems, however, not to be found at all in the Lias. 



