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DIVISION IV. ORTHOCER ACEiE . 



GENERA. 



A siphon extending Very abundant, es- 

 from the summit of the pecially in strata of 

 exterior to the same part Chalk and Compact 

 of the interior cone, Limestone. 

 whence it continues ei- 

 ther along the edge or 

 through the centre of the 

 septa. 



4. Belemnites. Boet. de 

 Boot. 



A thin double case, 

 composed of two cones 

 united at their bases ; 

 the interior cone much 

 shorter than the other, 

 divided within by paral- 

 lel septa, concave towards 

 the base ; only one cham- 

 ber (conical) apparent, the 

 older ones being succes- 

 sively effaced by the piling 

 up and contiguity of the 

 septa. PL 1, fig. 9, 22, etc. 



a. Elongated in cylinders, sharpened at the end only. 



b. Narrowed towards the base, like a distaff or lance. 



2. Orthoceratites. Brej- 

 nius. 



Straight or slightly bent 

 chambered; margins of lateral, 

 the septa even, or with 1 

 or 2 small undulations. 

 PL l,fig. 25. PL 2, fig. 

 11. 



A siphon central 



or Said to characterise 

 the Transition Rocks of 

 Werner. 



3. Conul aretes. Miller. 



Concave, hollow, mouth 

 half closed by an inflexion 

 of the lip. P1.3,fig. 19,21. 



4. Amplexites. Sowerby. 



di- 



Septa imperforate. 



In Transition Lime-' 

 stone, in Ironstone 

 Schale, with 

 shells. 



m 



marine 



Nearly cylindrical; 

 vided into chambers 



by 



numerous transverse sep- 

 ta embracing each other 

 with their reflected mar- 

 gins. PL 2, fig. 10. 



5. Nodosaria. Lam. 



Straight, chambered, 

 slender, with a contrac- 

 tion at each septum. 



In the Limestone of 

 the Black Rock at Lime- 

 rick. 



Akin to the Raphanis- 

 ter (PL 2, fig. 15), Echid- 

 nas (PL 2, fig. 14), and 

 Telebois (PL 3, fig. 22) 

 ofMontfort? 5 



B 



