120 



BRITISH BELEMNITES. 



Phragmocone. Known in a crushed state by specimens from near Chippenham. 

 The uncrushed phragmocone has a slightly elHptical section. D'Orbigny gives a very 

 elUptical section (55 to 45). The characteristic angle, as given by D'Orbigny, is 16° 30'. 

 I have no good specimen of this part of the fossil. 



Locality. In the Oxford Clay of Wiltshire, Oxfordshire, Northamptonshire, Hunt- 

 ingdonshire. In the Kelloway Rock of Yorkshire. In the Oxford Clay at Vaches-Noires 

 (Calvados), and Marquise, near Boulogne. 



Observatmis. Specimens are often found invested with a sheath of white fibrous 

 matter, externally rough and of granular aspect, within which the true shell is always 

 smooth and shining. 



I remark the following varieties : 



1. Belemnites Owenii (Puzosianus). PL XXXI, fig. 76 ; PI. XXXII, figs. 78, 79. 



The guard is smooth and always compressed ; the apicial furrow distinct or faint, 

 never more than half the length of the axis ; alveolar section elliptical. This is the ordi- 

 nary form from the Oxford Clay of the Midland Counties. In one middle-aged specimen, 

 corresponding to B. attenuatus of Mantell, lateral grooves extend all along the post-alveolar 

 tract. 



2. Belemnites Owenii (verrucosus). PI. XXXI, fig. 77. 



The surface is ornamented with small, raised, smooth puncta, and undulations com- 

 posed of these miited. The distribution of these may be seen on the ventral face (u), the 

 lateral (/'), and the dorsal {d'). On the first it will be noticed that the puncta disappear 

 towards the apex, and diverge and disappear on the alveolar region. On the sides they 

 show more of a tendency to gather in linear groups ; on the back this concurrence of the 

 puncta makes short undulated ridges, which grow larger, but more dispersed, on the 

 alveolar region. Tiie apex shows signs of very short plications. Only one specimen is 

 known to me, found by Mr. J. E. Walker, at St. Neot's, with Ammonites Duncani. The 

 reader may compare the curious granulation in this specimen with that on B. wfimdibulum 

 (PI. I, fig. 3), with that on specimens of Belernnitella granulata, and with the diverging 

 ornaments on a Sepiostarium. 



If further research should produce additional specimens, possibly there may be found 

 reason to adopt a specific name for this fossil. But the surface-ornament being at present 

 the only difference observed between this guard and ordinary specimens of B. Owenii of 

 the same size, I prefer to mark it as a variety. 



