BELEMNITES OF THE OXFORD CLAY. 



Ill 



Oolites {TIastati and Canalictdali) ; the others {Jornaliles and Exccntric'i) now first make 

 their appearance, to replace (perhaps we may say) the Giganlci, which they, however, 

 resemble in no particular except size. 



Belemnites hastatus, Blainville. PI. XXVIII, figs. C7 — 70. 



Reference. Var. a. Belemnites hastatus, Blainville, 'Mem. sur les Bclemn.,' p. 71, 



pi. 2, fig. 4, 4 «. 1S27. 

 Belemnites semihastatus, Blainv., ' Mem. sur les Bclemn.,' p. 72, 



pi. ii, fig. 5, 5a— 5<7. 1827. 

 Belemnites gracilis, Phillips, ' Geol. of Yorkshire,' vol. i, p. 1:38, 



pi. V, fig. 15. 1829. 

 Belemnites hastatus, D'Orb., ' Terr. Jurass.,' p. 121, pi. xviii, 



fig. 1, 9. 1842. (Exclude some of the synonyms.) 

 Beleinnites hastatus, Quenstcdt, ' Cephalopoda,' p. 412, pi. xxix, 



fig. 27—39. 1849. 

 Belemnites semihastatus rotundas, Quenstcdt, ' Cephal.,' p. 440, 



pi. xxix, fig. 8—11. 1849. 

 Belemnites semihastatus depressus, Quenstcdt, ' Cephal.,' p. 440, 



pi. xxix, fig. 12—18. 1849. 



Guard. Very elongate, smooth, hastate, with an acute apex (by decay of lamin;c 

 about the alveolar apex it becomes fusiform) ; in all stages of life depressed and expanded 

 laterally in the post-alveolar region ; cylindrical or somewhat compressed about the alveolus ; 

 ventral surface marked by a distinct groove, which is extended forward over the alveolar 

 cavity, and backwards toward the apex, about half the length of the axis of the guard, so 

 as to leave much of the expanded part free from groove, or with merely a faint indication 

 or trace of groove. In young specimens this part appears swollen on the ventral aspect 

 (see fig. 69, 2^, 2*). 



Transverse sections show the laminae of the guard thickening on the dorsal aspect of the 

 alveolar cavity, so as to make the section circular, or a little oblong there ; the sectional out- 

 line is depressed and reniform in the post-alveolar region, till the bulbous part is reached, 

 which has an oval section gradually growing circular toward the conical or slightly sub- 

 mucronate point. The axis is nearly central. In some excellent specimens are small faint 

 longitudinal bent or sigmoidal furrows one on each side of the guard. They begin nearer 

 to the ventral than the dorsal surface, and bend upward before losing their distinctness 

 (figs. 68/', 07/). 



Dimensions. In the Oxford district within a few miles of the city, the clay-pits have 

 been well searched for these Belemnites, and with great success as far as the young 



