BELEMNITES OF THE LIAS. 41 



Belemnites compressus, staid. PI. Ill, fig. 8. 



Beference. Belemnites compressus, Stalil, ' Correspondenzblatt der Wiirt. Landw. 

 Vereins,' pi. xxxiii, fig. 4, 1824. 

 B. Fournelianus, D'Orb., 'Terr. Jur.', p. 97, pi. x, figs. 7—14, 1842. 

 B. compressus, Quenstedt, 'Ceplial.,' p. 405, pi. xxiv, figs. 18, 19, 1849. 



Guard. Much compressed, expanded posteriorly, and ending in an obtuse or rounded 

 apex ; anteriorly contracted, and sometimes quadrate over the alveolar region. In some 

 specimens the obtuse point is replaced by a cavity plaited at the edges, as in B. umbilicatus 

 of Blainville. From the apex a short broad groove proceeds nearly along the middle of 

 each side, and extends towards the alveolar region. On that region one distinct, narrow, 

 dorso-lateral groove appears, and extends towards the apex ; a short broad groove is also 

 seen in some specimens on the anterior part of the ventral face of the alveolar region. 



Transverse sections show an oval outline and a nearly central axis. 



Greatest length observed, 2 inches ; but it grows to greater length. (Quenstedt, 

 ' Cephal.,' pi. xxiv, fig. 18.) 



Proportions. The diameter, v d, at the apex of the alveolus being taken at 100, the 

 ventral part is 48, the dorsal 52, the transverse diameter 75, and the axis about 300. 

 This proportion of the axis varies ; the individuals with longest axis are supposed by 

 D'Orbingy to be males. 



Phragmocone unknown. The alveolar angle is 28°. 



Variations. Considerable, in regard to the completeness of the grooves and striations 

 and the degree of expansion near the apex. A cm'ious monstrosity occurs among Mr. 

 Moore's specimens from llminster. In some specimens from Lyme two parallel narrow 

 grooves appear on each side ; in others one broad shallow groove only. 



Locality. Lyme Regis, in Belemnite-beds of Middle Lias {Geol. Survey). Glaston- 

 bury, in Middle Lias {Oxford Museum). llminster. Middle Lias [Moore). I have seen 

 no specimen on the coast of Yorkshire. 



Belemnites breviformis, Voltz. PI. IV, figs. 9 a, 9 b, 10a, 10 b, 10 c, 10 d. 



Beference. B. hreviformis, Voltz, ' Obser. s. Belem.,' p. 43, pi. ii, figs. 2, 3, 4, 1830. 

 B. breviformis amalthei,QL\\.tVi&\jt^\, 'Cephal.,' p. 405, pi. xxiv, figs. 21 — 23, 

 1849. 



Guard. Short, lanceolate, cylindroidal, subtetragonal, tapering to a pointed summit, 

 which is more or less recurved towards the back. 



