CRICK : ARMS OF THE BELEMNITE. 273 



is presented is either ventral or dorsal. The attempt to determine 

 whether the view that is presented is dorsal or ventral, is based upon 

 the fact that the pro-ostracum was situated principall)' on the dorsal 

 side of the ink-bag ; when, therefore, the pro-ostracum is seen to rest 

 upon the ink-bag, a dorsal aspect of the fossil is probably presented, 

 but if it passes beneath the ink-bag a ventral aspect of the fossil is 

 probably exposed. If no remains of the pro-ostracum are visible 

 either upon or beneath the ink-bag, the aspect of the specimen is most 

 probably ventral, though it may possibly be dorsal, in which case the 

 pro-ostracum would have been removed. 



With respect to the order of the arms the present writer has not 

 been able to arrive at a satisfactory conclusion. The longest pair of 

 arms was lateral, but of the other two pairs it is somewhat uncertain 

 which was dorsal and which ventral. The writer believes, however, 

 that the medium- sized pair was dorsal, and the shortest pair ventral. 



The fossils in which the six uucinated arms have been seen are 

 described below. The arms being almost symmetrically placed, and 

 also well preserved in the type-specimen of Belemnoteuthis Montejiorei, 

 this fossil is described first. 



Specimen No. 1 (PI. XXIII, Fig. 2). — This is Professor James 

 Buckman's type-specimen of Belemnoteuthis Montefiorei, from the 

 Lower Lias shales between Charraouth and Lyme Regis [B.M. No. C. 

 5,026]. It was originally figured by that author,' and has since 

 been refigured by the present writer." Professor Buckman described 

 the fossil as nearly 12 inches in length. It is now at most only 

 10 inches ( = 254 mm.) long, and, as the present writer has already 

 explained elsewhere, when Professor Buckman's figure was drawn the 

 uppermost portion of the slab containing the arms was so placed that 

 the arms were at right angles to the rest of the body, but since then 

 this part of the slab has been detached and replaced in such a manner 

 that the arms now have the same general direction as the rest of the 

 body. From the base of the arms to the posterior boundary of 

 the ink-bag measures 126 mm. Although the relative position of the 

 booklets in the outermost row on each side is not quite so clearly 

 indicated as in the rest, there are six double rows of booklets, 

 indicating six arms. These are almost symmetrically disposed, and 

 occupy an angle of about 60° or 7U°. The two outermost arms {a, f) 

 are longer than the rest; they were apparently more slender and 

 had their booklets more sparsely distributed than the remaining four 

 arms ; of the latter the two outer ones {b, e) are a little longer than 

 the others {c, d). The arms of the specimen can be grouped in three 

 pairs; the first pair consists of the two outermost arms («,/), each 

 being about 60 mm. long or possibly more, since they appear to be 

 interru{)ted by the edge of the slab bearing the specimen ; the second 

 pair includes the two intermediate arras {h, e), each about 46 mm. 



1 J. Buckman: Proc. Dorset Nat. Hist. & Antiq. Field Club, vol. iii (1879), 



pp. 141-3, plate facing p. 142. 



2 G. C. Crick : Froc. Malac. Soc, vol. v, pt. 1 (AprO, 1902), pp. 13-16, pi. i. 



VOL. VII. — JUNE, 1907. ^^ 



