50 BRITISH BELEMNITES. 



Greatest length observed, 5'5 inches ; greatest diameter, 0-85 ; axis of guard, 4 inches. 

 Proportions. The diameter {v d) at the alveolar apex being 100, the ventral radius 

 is 37 to 40, the dorsal radius 60 to 63, the diameter from side to side 88, axis 450 to 600. 



Phragmocone. Oblique, incurved ventrally, with oblique septa, and an elliptically 

 compressed section ; the dorsal and ventral faces (curved) inclined at an angle of 29°, the 

 lateral faces (straight) at 25°. On the alveolar shell the dorsal region is defined by a 

 somewhat prominent longitudinal line. If the diameter {v d) of the largest chamber be 

 taken at 100, the diameter from side to side = 90, the depth of the chamber = 12, and the 

 longest side of the alveolus 300. The axis of the phragmocone = half the axis of the guard. 



Localities. The Belemnite-bed, base of Middle Lias, at foot of Golden Cap, Lyme 

 Regis {Miss Anning). Cheltenham {Strickland). 



Observations. Described by Brongniart as from Lyme Regis in 1826. It has been 

 referred by D'Orbigny to B. compressus of Blainville, but its true affinity is to ^. 

 elongatus, as given by Sowerby, and to B. paxillosus of Voltz. It varies as to the degree of 

 lateral compression and as to the terminal plaits and striae. 



Belemnites elongatus, Soioerby. PI. VII, fig. 17. 



Beference. Sowerby, 'Min. Conch.,' p. 178, t. 590, fig. 1, 1828. 

 Quenstedt, ' Cephal.,' p. 402, t. 24, fig. 3, 1849. 



Huxley, in * Memoirs of the Geological Survey,' Monograph II, pi. i, 

 figs. 2, 3, 1864. 



Guard. Rather compressed, cylindroidal about the apex of the phragmocone, thence 

 tapering in regular sweep to the acute-angled point, and expanded towards the aperture ; 

 dorso-lateral grooves distinct for only one fourth or one third of the length of the axis, 

 thence obscurely prolonged into the somewhat flattened sides ; small plaits, striations, and 

 granulations on the surface, especially near the apex ; no ventral furrow ; axis a little 

 excentric, most so at the apex of the phragmocone. 



Sections show the axis excentric, within a slightly oval outhne, and nearly straight. 



The largest individual yet observed is the fine specimen figured by Sowerby, and now 

 preserved in the British Museum, which is complete from the apex to the last or nearly 

 the last septum of the chambered cone, and measures 10! inches in length. Of this the 

 axis of the guard is about 3 inches, that of the phragmocone nearly 8 inches ; longest 

 diameter of section at the apex of phragmocone, 09 inch. My smallest specimen from 

 Lyme Regis measures 0-38 inch diameter, and 165 long. 



In this young individual the lateral grooves are quite chstinct, and continued to the 

 acutely tapered apex ; two striae appear on the dorsal aspect at the apex, and one small 

 plait on the ventral aspect. 



Proportions. Taking the dorso-ventral diameter at 100, the ventral radius is 40, the 



