[137J CEPHALOPODS OF NORTHEASTERN COAST OF AMERICA. 347 



canary -yellow ones. On tbe lower side they are so thinly scattered 

 that they leave much of the translucent bluish white ground-color visi- 

 ble between them ; along the median ventral line the spots are more 

 numerous, producing a distinct median stripe. The caudal hn is clear 

 bluish white beneath, aud very translucent, becoming almost transparent 

 near the margin. 



Exposed part of the siphon similar to the ventral surface of the body, 

 but with the spots more sparse, and mostly disappearing near the margin 

 and at the base ; lower side of the head, in front of the eyes, sparsely 

 spotted. Outer and upper sides of the upper arms and outer surfaces 

 of the ventral pair similarly, but somewhat more densely, specked ; both 

 sides of the ventral arms and lower sides of the lateral arms pinkish 

 white and unspotted. Tentacular arms pale translucent, bluish white, 

 with the outer surface, except at base, rather thinly specked with small 

 purplish chromatophores ; the inner surface and upper side of the tip 

 and the suckers are translucent white ; rings of suckers white. 



On the inner surface of the dorsal and lateral arm*, between the 

 suckers, there are a few large chromatopkores, and a double row of them 

 runs out obliquely on the muscular thickenings of the marginal mem- 

 brane, alternating with the suckers, on each side ; suckers pure trans- 

 lucent, bluish white (becoming yellow or brown in alcohol). 



The pupils of the eyes are deep bluish black; on the upper side they 

 are encroached upon by a sinuous downward extension of the iris, 

 which is silvery or pearly white, with brilliant, green, opalescent reflec- 

 tions at the upper margin. 



Sexual differences. 



Tbe sexes differ to a considerable extent in proportions. If we com- 

 pare specimens of equal length, the female will have the body relatively 

 stouter and less tapered posteriorly than the male; the head is decidedly 

 larger;* the arms are longer; the suckers are usually distinctly larger, 

 especially those of the tentacular arms. But if we compare specimens 

 having the head and arms of equal size, the male will be found to have 

 a decidedly longer, more slender, and more tapered body, and a some- 

 what longer and narrower fin. (See Table B, for comparative propor- 

 tions.) 



In the adult male the circumference of the head to the mantle-length 

 usually varies from 1 : 2.55 to 3.45, averaging about 1 : 3.10 ; in the female 

 from 1:1.75 to 1:2.45, averaging about 1:2.25. 



The ratio of the breadth of the fin to the mantle-length, in the male, 

 varies from 1 : 2.12 to 1 : 2.45, averaging about 1 : 2.25 ; in the female, from 

 1:1.70 to 1:2.12, averaging about 1:1.90. 



* Some of the nominal European species of Loligo, that have been based on the 

 smaller size of the head, arms, and suckers, are probably only the males of the common 

 species. The sexual variatious in this genus have apparently been very imperfectly 

 understood by European writers generally. 



