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PROCEEDINGS OF THE MALA.COLOGICAL SOCIETY. 



aspect of the head would have heen presented. In that case, however, 

 the third arm (e) would have heen the highest, and the fourth {d) the 

 lowest, lower even than the first {a) and the fifth {e), but this is 

 certainly not the case. The third arm {c) is the highest ; the fourth 

 arm (d) is almost on the same level, this being a little higher than the 

 second (b) and fifth {e). which again are higher than the first (a) and 

 sixth (/). On the other hand, if the third {c) and fourth (d) are 

 regarded as the shortest pair of arms, the second {b) and fifth {c) as 

 the medium-sized pair, and the first {a) and sixth (/) as the longest 

 pair, then it must be observed that the first {a) is much more extended 

 than the sixth (/), the second {b) than the fifth <e), and the third (c) 

 than the fourth {d) ; that is to say, the three arms on the left-hand 

 side of the fossil are more extended than the corresponding arms on 

 the right-hand side. On the whole, however, the latter rendering of 

 the order of the arms seems to be more probably correct. The ink- 

 bag bears on its surface fragments of the pro-ostracum, so that if 

 a dorsal aspect of the specimen is presented, and the present inter- 

 pretation of the relative position of the arras is correct, the third and 

 fourth (counting from the left) arms (c and d) are the two dorsal, the 

 second and fifth {b and e) the lateral, and the first and sixth (« and/) 

 the ventral. The arms b and e are regarded as the lateral, because 

 a and / seem to pass beneath them as though passing to the opposite 

 side of the head. 



Specimen No. 4 (PI. XXIII, Fig. 6). — This interesting specimen 

 [B.M. No. 47,716] is preserved on the surface of a small slab from 

 the Lias of Lyme Kegis. It shows the six arms aiTanged fan-shaped 

 in a sector, consisting of a little more than a semicircle. The arms are 

 all in the same plane ; the ink-bag is present, and beneath it are 

 remains of the pro-ostracum. The specimen is evidently very much 

 squeezed together because the duct of the ink-bag touches the_ bases of 

 the arms. The ink-bag with its duct is 45 mm. long, and its greatest 

 width 25 mm. The extreme bases of the arms are not preserved. 

 Six arms are very clearly shown, but the six do not occupy an angle 

 of more than about 200°. As only two of the arms [c and d) are 

 nearly complete and the others more or less imperfect, it is difficult 

 to recognize the arms belonging to each pair. Their arrangement, 

 however, appears to have been as they are now placed. Commencing 

 from the left, the first arm {a) is 25 mm. long, and is intercepted 

 distally by the edge of the slab ; its booklets are rather widely 

 separated. The second arm (b) is somewhat shorter, but this again is 

 imperfect distally. The third (c) appears to be about 30 mm. long, 

 and is nearly, but not quite, complete distally. The fourth {d) is 

 35 mm. long, and like the third [c) its distal end is nearly, but not 

 quite, complete. The fifth (^) is nearly of the same length as the 

 fourth {d), but is not nearly so complete distally; whilst the sixth 

 (/) seems to be at least 35 mm. long, but its distal end is not quite 

 complete. The pairs of arms in this specimen then seem to be af, be, 

 cd. The arms a and/ appear to have been the most slender, and may 

 have been either the shortest or the medium-sized pair, probably the 

 former, but each is interrupted distally by the edge of the slab on. 



