CRICK : ARMS OF THE BELEMNITE. 277 



which the fossil is preserved. The arms b and e were apparently the 

 stoutest, and, although in their present state shorter than c and d, 

 were most probably originally longer than those arms, and very 

 possibly were the longest pair of arms. The arms c and d are the 

 most nearly complete, and though somewhat stout, were possibly 

 either the shortest or the medium-sized pair, probably the latter. 

 In this example the ink-bag rests upon the pro-ostracum, so that in 

 all probability the ventral aspect of the animal is displayed. If an 

 oral aspect of the arms is presented, and if the identification of the 

 order of the arms is correct, the medium-sized pair of arms (c and d) 

 was dorsal ; the longest {b and c), lateral ; and the shortest (« and /), 

 ventral. Judging from the appearance of the booklets, the arms may 

 present their outer surface, as if the head with the arms spread out 

 had been turned towards the dorsal surface with the mouth down- 

 wards, in which case the medium-sized pair of arms would be ventral, 

 and the shortest dorsal. 



Specimen No. 5 (PI. XXIII, Fig. 5). — This example [B.M. 

 Xo. 47,020], preserved on the surface of a slab from the Lias of Lyme 

 Regis, shows the arms arranged in a fan-shaped manner, with a small 

 portion of a dark-brownish material at their base (apparently the 

 remains of the jaws), the ink-bag, and portions of the mantle and of 

 the pro-ostracum. The distance from the base of the ink-bag to the 

 base of the arms is 135 mm. The arms vary in length, but are rather 

 difficult to arrange in pairs. Commencing on the left, the first arm («), 

 traceable for a length of about 22 mm., is imperfect distally, and 

 proximally coalesces with the second arm. At a distance of about 

 5 mm. from its distal end there is the detached proximal end of an 

 arm, about 12 mm. long, that appears to have belonged to this first 

 arm. The second arm {b) is 40 mm. long, and seems to be nearly 

 complete, at both its proximal and its distal end. The third arm {c) 

 seems to be stouter than either the first or the second ; it is about 

 22 mm. long, and is obviously imperfect at its distal end ; immediately 

 above it, and at a distance of about 10 mm. from it, there are a few 

 detached booklets, which seem to have belonged to this arm. The 

 fourth arm {d) appears to have been about 32 mm. long, the booklets 

 being very clearly shown for a length of 28 mm.; its inner aspect 

 seems to be displayed, the arrangement of the booklets on the arm 

 being particularly well shown. The fifth arm {e), about 32 mm. long, 

 is not quite complete distally ; proximally it coalesces with the sixth 

 arm (/). The sixth arm (/) is about 40 mm. long and incomplete 

 distally. Judging by the position of one or two of the hooklets near 

 the proximal end of the sixth arm, this arm appears to pass under the 

 fifth arm {e) ; a booklet near the base of the fifth arm {e) rests upon 

 a booklet of the fourth {d), and one or two of the third (c) certainly 

 rest upon the fourth {d), whilst near the proximal end a booklet 

 apparently belonging to the first arm («) certainly passes beneath the 

 second arm (b). In this view of the head, therefore, the smallest pair, 

 c and d, appear to be at the back, the medium-sized pair, b and e, in 

 the front, and the longest pair, a and /, at the sides. The ink-bag 

 bears upon its surface remains of the muscular portion of the animal 



