Semirossia patagonica (E. A. Smith 1881)

ROSSIA PATAGONICA, sp. n. (Plate III. figs. 3, 3a.)

Animal, viewed dorsally, of a purplish slate-colour. This is composed of a vast aggregation of minute irregularly shaped dots set upon a pale buff ground, which is more apparent upon the fins, as there the dotting is less dense. Lower or ventral surface of a reddish-purple color and the dotting more defined than above. The underside of the head light buff, with only a few large subcircular spots, of the same hue as those on the body. The lower surface of the fins and the funnel are of a plain buff. The abdomen or body is in form like a short sack, narrowing and rounded at the the end, about half as long again as broad. Its margin is produced to au obtuse point over the back of the neck, which marks the termination of the horny shell; and on the underside there is a wide sinuation beneath the siphon.

The fins are moderately large, being to the length of the body as 5 to 7; but the line of junction is somewhat less, for they extend forward about a line and a half beyond the point of contact. In form they are irregularly semicircular, and are placed rather far apart, but yet not absolutely along the side. Their surface, both above and beneath, exhibits fine striæ which radiate from the body.

The head is large, as broad as the body. The eyes are situated at the sides of the head, and are protected by a thin transparent membrane, and the lower margin is probably partly contractile over the eye.

The arms do not vary much in length; but the dorsal and ventral pairs are a trifle shorter than the two lateral pairs. They are rather slender, and taper to a fine point, scarcely have any interbrachial connecting membrane at their base; and between the ventral pair there is a total absence of it.

The suckers are large, subspherical, raised upon prominences, connected by excessively short peduncles, and armed with very small simple-edged horny rings. They are arranged in two alternating rows, except upon that which is the right arm of the dorsal pair when the lower or ventral surface is towards the eye, or the left one when viewed from above; upon this there are four series at the central part, but fewer at the base and the extremity; the suckers too are much smaller than those upon the rest of the brachia, with the exception of the other dorsal one, upon which they are also equally small.

The tentacular arms are slender, twice as long as the others, and emerge between the ventral and next pair of arms, between which there is a greater development of connecting membrane than is found between the other brachia. They are provided at the ends with numerous crowded cup-like acetabula, raised upon longer footstalks than those connecting the suckers of the other arms. They are flat-topped, with a raised outer rim and a sunken lid, and the horny margin of the orifice is minutely dentate. Shell or gladius very minute.

The measurements are:--Length of body 21 millims., diam. 14; length of fins 14 millims., diam. 8; length of longest arm 17 millims.; length of tentacular arm 36 millims.; length from the end of the body to the base of the ventral pair of arms 27 millims.; the same to the base of the dorsal pair 29 millims.; diam. of one of the largest spherical suckers 1 ½ millim.; diam. of one of the small ones on the right dorsal arm ¾.

Hab. Stations 1 and 5.

This is a very remarkable little creature, and at once recognized by the peculiarity of one of the arms possessing a double set of suckers.”

(Smith, 1881: 22-24)

Semirossia patagonica is a species of bobtail squid native to the southwestern Atlantic Ocean and southeastern Pacific Ocean; it occurs around the southern part of South America and has been recorded from waters off Chile, Anegada Bay, Tierra del Fuego, Argentina, and the Falkland Islands.

The type specimen measures 21 mm in mantle length (given as "Length of body 21 millims.").

The type specimen was collected off Patagonia, Argentina and is deposited at The Natural History Museum in London.