.4. E. Verrill — North American Cephalopods. 
309 
LoligO Pealei Lesueur (continued). 
Tryon, Man. Conch., p. 143, PI. 52, figs. 141, 142, (descr., and figs, copied from pre- 
ceding). 
Terrill, Amer. Journ. Sci., xix, p. 292, 1880. 
Plate XXIX, figs. 1-4. Plate XXXTII, figs. 1-3 (pens). Plate XXXIX, fig. 4 
(odontophore). Plate XL (anatomy). Plate XLI (anatomy and young). Plate 
XLT, FIGS. 3, 4 (young). 
Body rather elongated, more or less stout, according to state of 
distention or contraction,* tapering backward to a moderately acute 
posterior end, more acute in the male than in the female. Caudal 
fin long-rhomboidal, with the outer angles very obtusely rounded ; and 
varying, according to age, in the ratio of its length to its breadth, 
and greatly, also, in the proportion that its length bears to that of 
the mantle.f The length of the caudal fin, in proportion to that of 
the body (mantle), although variable, normally increases with age, 
even after sexual maturity. In this species, with specimens having 
the mantle from 100 to 125 mm long, the ratio of the fin to the mantle 
usually varies from 1 : V80 to 1 : 1*90; with the mantle 150 to l75 mm 
long, the ratio usually becomes 1 : T65 to 1 : T75 ; in the largest 
specimens, with the mantle, 260 to 400 mm long, the ratio varies from 
1 : T50 to 1 : 1-65, rarely becoming 1 : 1-75. The ratio of the breadth 
of the caudal fin to the length of the mantle, in the larger male 
specimens, ranges from 1:2-12 to 1:2*40, varying considerably 
according to the mode of preservation ; in the larger females it 
varies from 1 : 1-70 to 1 : 2-12. 
The anterior ventral edge of the mantle recedes, in front of the 
siphon, in a broad curve, leaving an obtuse angle at either side, oppo- 
site the lateral cartilages; from these angles it again recedes, on the 
sides, in a concave line, and then projects considerably forward, form- 
ing a prominent, median, dorsal lobe, which gradually tapers from 
the base, and then rather suddenly narrows to a point, over the end 
of the pen ; the point, when in its normal position, reaches as far 
* The mantle, when the gill-cavity is distended with water, lias a larger size than 
when the water is expelled by the contraction of its walls, which is usually the con- 
dition in which specimens die. Moreover, when the large stomach is distended with 
food, and when the ovary is distended, in the breeding season, with eggs, the form is 
stouter than usual. 
f This variation is largely independent of sex, and is due partly to the ordinary 
changes during growth ; partly to the condition of the muscular tissues at the time of 
death ; and partly to the effects of the alcohol in which they have been preserved. 
These latter causes, in the case of preserved specimens, more or less obscure the 
effects of growth in causing the proportions to change. 
