158 PROF, OWEN ON NEW AND RARE CEPHALOPODA. 
than that covering the rest of the arm; the breadth of the marginal fold along the 
basal 12 inches of the arm (Pl. XXXYV. fig. 2, c) is about 20 millims. The surface of 
the fold towards the non-acetabuliferous part of the arm shows the same deep colour 
as that part. The opposite surface of the fold continued from the acetabuliferous 
tract has the paler tint of that tract. The contrast was doubtless greater in the living 
Squid, when the pigment was in lively motion along the free surface. 
In the interspace of two cups of the same side the integument shows two low folds 
or risings, produced by a pair of muscular bundles detached from the mid-acetabuli- 
ferous space to the edge of the ectacetabular fold, for the contraction or narrowing of 
that fold. Each dorso-marginal fold (Pl. XXXIV. fig. 1, 6, 6) shows a breadth of about 
2 inches as far as where it extends along the middle third of the length of the arm; 
thence the breadth gradually decreases; and the folds finally subside about 4 inches 
from the end of the arm (ib. fig. 2). 
The total length of the above-described cephalic arm (one of the ordinary eight) is, 
I may repeat, 9 feet; its circumference at mid-length, folds inclusive, is 9 inches; the 
number of acetabula which it supports is not less than two hundred and ninety-two. 
The known species of the Loliginide vary in the relative length of the arms to the 
body. In Loligo vulgaris, Lam.1, the length of the longest is about one half of the 
body, measured from the end of the anterior prominence of the dorsal margin to the 
posterior apex of the mantle. In Ommastrephes duvaucellii, d’Orb.*, the length of the 
same arm is four fifths that of the body or trunk similarly measured. In Loligo todarus* 
the length of the same arm is equal to five sixths that of the body. According to the 
latter standard the length of the body of our Plectoteuthis may be estimated at 10 feet 
6 inches, according to the first standard at 18 feet. In both estimates the length of 
the head, or part intervening between the trunk and origin of the arms, must be added ; 
it is commonly one third the length of the trunk. If this be taken at 18 feet, the 
total length of Plectoteuthis grandis may have been 33 feet. 
The above-described material evidence of the huge dimensions attained by certain 
species of Cephalopoda has long formed part of the stores in the British Museum ; and 
there is no note or record of its origin’. JI proceed, therefore, next to notice similar 
large specimens of which the localities are known. 
Of these a satisfactory and instructive instance is the following:—In the general 
observations on the fauna of the isles of St. Paul and Amsterdam by the accomplished 
zoological member of the French expedition of the “Transit of Venus” (9th December, 
1874), M. Ch. Vélain states that “at the early part of November in that year a tidal 
wave stranded on the north shore of the Isle of St. Paul a Teuthid of the group of 
1 D’Orbigny, op. cit. Loligo, pl. 22; the arms are somewhat shorter relatively in the Squid figured as 
L. vulgaris in pl. 8. ? Op. eit. Loligo, pl. 14. * Op. cit. Loligo, pl. 1. 
* Tt is briefly referred to by Mr. W. Saville Kent, F.L.S., in the ‘ Proceedings of the Zoological Society,’ 
March 1874, p. 179, 
