﻿CLASSIFICATION. 



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Especially in the anterior part and in the circle of hooked arms Mr. Day's specimens 

 have been found very suggestive. The arms are, on the whole, unexpectedly short (as 

 compared with those of Belemnoteuthis) ; the head also, with the eyes, appears smaller in 

 proportion than among other Cephalopoda, and the whole body seems longer in pro- 

 portion than is usual among them, in this respect more resembling the Calamaries (Loligo) 

 than the Cuttles (Sepia). 



CLASSIFICATION OF THE BELEMNITID^E. 



To the earlier writers the family of the Belemnitidse was known only by the two 

 prominent examples now called Belemnites and Belemnitella, and of these they knew not 

 the whole. The chambered cone was not always clearly understood as an essential and 

 very characteristic part of the whole shell until Klein (1731) gave forth his ' Descriptions 

 Tubulorum Marinorum/ which include Orthoceratites. In this essay Belemnites 

 constitute the eleventh genus of Tubuli Marini, and are thus clearly defined : 



" Belemnites est tubulus marinus ; fossilis ; materiae ad Seleniticam accedentis ; teres ; 

 transversim fractus concentricis striis, in longitudinem fissus canaliculo pervio, semper in 

 medio posito, donatus ; in basi nonnunquam ferens conum, olim testaceum, concameratum, 

 instructum siphunculo." 



This cone was, and still often is, called the alveolus, though that name properly 

 belongs to the conical cavity. The siphuncle of this chambered shell is regarded by Klein 

 as connected with the central canal of the guard, and with a globule at its apex. He 

 founds this opinion chiefly on specimens from the Chalk, and compares this structure to 

 that of the chambered Nautilus crassus, distinguishing this from the open-shelled 

 Argonaut. In agreement with previous writers, he distributes Belemnites into three 

 groups — cylindric, conical, fusiform. 



Fifty years afterwards, Miller, satisfied himself of the affinity of Belemnites to the 

 shelly parts of Cephalopoda, perceived the analogy of the animal to which the fossil be- 

 longed with the recent possessor of the " Cuttle-fish bone," and presented a conjectural 

 drawing to illustrate the generic character, which is in these words : 



Genus. Belemnites. — A cephalopodous ? molluscous animal, provided with a fibrous, 

 spathose, conical shell, divided by transverse concave septa into separate cells or chambers 

 connected by a siphuncle, and inserted into a laminar, solid, fibrous, spathose, subconical 

 or fusiform body extending beyond it, and forming a protecting sheath or guard. (' Geol. 

 Trans./ 2nd series, vol. ii, p. 48.) 



It is unnecessary now to notice his genus " Actinocamax," which is only the retral 

 portion of the guard of a Chalk or Gault Belemnite, separated at or near the apex of the 

 phragmocone — often by natural decay of the shelly lamina?. 



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