A. E. Verrill — North American Cephalopods. 309 



LiOligO Pealei Lesueur (continued). 



Tr^'on, Man. Conch., p. 143, PI. 52, figs. 141, 142, (descr., and figs, copied from pre- 

 ceding). 

 Yerrill, Amer. Journ. Sci., xix, p. 292, 1880. 



Plate XXIX, figs. 1-4. Plate XXXVII, figs. 1-3 (pens). Plate XXXIX, fig. 4 

 (odontophore). Plate XL (anatomy). Plate XLI (anatomy and young). Plate 

 XLV, 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"'"' long, the ratio of the fin to the mantle 

 usually varies from 1 : 1-80 to 1 : 1-90 ; with the mantle 150 to 175"'"' 

 long, the ratio usually becomes 1 : 1'65 to 1 : 1*75; in the largest 

 specimens, with the mantle, 260 to 400""" long, the ratio varies from 

 1 : 1-50 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, ojjpo- 

 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, wdiich 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-cavitj- is distended with water, has a larger size than 

 wheii 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. 



