BELEMNITES OF THE OXFORD CLAY. 



II 



retains the distinct names, and is, in this respect, in agreement with other Geiuian 

 writers. Collections in Germany follow this model in their arrangements. D'Orbigny 

 joins to these Bdemnites fusiformis of several writers, B. ferriiginem of Voltz, and 

 B. (jracilis of Raspail. 



In considering the varieties to which the species seems liable, we find among English 

 specimens, of lengths from half an inch to three inches, some differences in the general 

 shape of the guard, which in some specimens is elegantly hastate (fig. 69, v"), in others 

 more expanded and recurved at the apex (fig. 69, V\ v'), in a few bulbiform 

 (fig. 69, y", V'), in one deformed (fig. 70, ^). The ventral groove is generally 

 absent from half of the length of the axis of the guard ; in rare cases (fig. 69, v') it is 

 interrupted, sometimes it leaves more than half of the length of the axis of the guard 

 smooth. I do not observe lateral fnrrows on any of the small specimens, and it seems 

 rarely absent from any of the larger ones. In the older form, which exceeds six inches 

 in length, the undulated, or somewhat oblique faint double furrow, is traceable nearly as 

 D'Orbigny has represented it ('Terr. Jur.,' pi. xviii, fig. 4). 



Belemnites hastatus, var. bulbosus. PI. XXVIII, fig. 69, v^, v'. 



The variety to which attention is now called, is more than any other remarkable for 

 the retral expansion of the guard and the swollen ventral outline of the expanded part. 

 In eleven specimens before me, including individuals from \ inch to 2\, the characters wore 

 nearly uniform. The broad part of the guartl is about ird of the axis from the apex ; the 

 groove usually terminates at half the length of the axis from the apex ; but in one 

 specimen (fig. 69, v^) it is interrupted and fiirther extended. 



The sections are nearly round in and for a small space behind the alveolar portion, 

 but everywhere further back they are/clliptical. The laminas over and a little behind the 

 alveolar space are, as usual, pale and less calcareous than in the more solid part of the guard. 



Localily. Specimens of this very interesting form have been forwarded to me by 

 Mr. J. F. Walker, of Sidney Sussex College, Cambridge, from the Oxford Clay of 

 St. Ives, Cambridgeshire, where they are accompanied by B. Puzosianus of D'Orbigny, 

 and B. sulcatus of Miller. 



I have examined in foreign collections a considerable number of specimens called B. 

 hastatus and B. semihastatus, and considered the figures which are given as representing 

 them. I am unable to perceive differences among them or among the com[)arativeIy few 

 English examples of full size, such as to require the employment of more than one 

 specific name. At the same time there are differences; some have a nearly circular 

 section across the expanded part of the guard, others a depressed contour there ; similar 

 variations occur in the alveolar region. To the former the ' variety-name ' of rofinnlun 

 has been assigned, to the latter dejjrcssus. The somewhat flcxuous lateral groove is 

 absent in some and present in other examples not otherwise dificring. 



