24 



CRUSTACEA MALACOSTRACA. II. 



11907. Psciidotavais forciptifus Vaiihoffen, Zool. Jahrbiicher, Abth. fiir Sy.st., Bd. XXV, p. 511; Taf. 20, 



fig. 10—12 (Adult Male). 



Female. Sars lia.s publi.shed a good description with iiuinerou.s figures of this sex. To his 

 description mav be added that the front margin of the head, seen from above, is shaped as in 

 P.Lilljrborgii (comp. fig. 5 a), thus nearly transverse, feebly convex at the middle, not emarginate at 

 the antennulas, and the antero-lateral angles not produced. 



The female is readily distinguished from the other northern species, excepting P. abyssi n. sp., 

 by the strongly forcipate chelae; from P. abyssi it is separated by having no pleopods, the uropods 

 much shorter, the antennulie and the walking legs shorter and thicker, etc. 



Sub adult Male. It has been figured and mentioned by .Sars, who erroneously considered it 

 the adult male. It agrees with the female in the shape of the chelse, the antennulse, the distal joints 

 of the thoracic legs, etc., but it differs in three features: fourth and fifth thoracic segments shorter, 

 but abdomen proportionately longer and thicker than in the female, and the pleopods well developed 

 with long setEe. — In younger male specimens the thoracic and abdominal segments are more similar 

 to those of the female, while the pleopods are smaller with the setaa short. 



Adult Male. Almost fifty years ago Lilljeborg published a brief description in the Swedish 

 language of this sex, but did not figure it, and some five years ago Vanhoffen (1. c.) pointed out the 

 main differences between female and adult male, with three analytical figures of male appendages. \ 

 more full description may be given here. 



The anterior end of the liead about half as broad as the carapace (fig. 3a); the front margin 

 is deeply emarginate at the base of each antenuula (fig. 3 c) and the antero-lateral angles considerably 

 produced with the end blunt; in a lateral view (fig. 3 b) the head is produced forwards covering the 

 base of the outer side of the antennula as a rounded plate. 



The antennulse are seven-jointed (figs. 3b and 3c); the two proximal joints are very thick, 

 subequal in length and together a little longer than the five others combined ; third joint broad and 

 a little longer than the two next joints combined ; fourth joint very short, with a tuft of sensory 

 hairs on the lower distal angle; the four distal joints increase considerably in length and decrease in 

 thickness from the fourth to the seventh; fifth and sixth joints with some sensory hairs at the outer 

 distal angle; seventh joint considerably longer than the sixth. 



The cheke (fig. 3 b) are a little more than twice as long as broad and differ much from those of 

 the female; the fixed finger at the base twice as broad as the movable, but the major distal part of 

 its incisive margin is so concave, that a conspicuous interval is seen between the fingers when their 

 terminal parts cross each other. The movable finger is evenly curved, somewhat longer than the 

 front margin of the hand; the inner surface of the hand has above the insertion of the movable finger 

 a transverse row of about nine peculiar setae. 



Fifth thoracic segment (fig. 3 a) a little shorter than the two preceding segments combined and 

 as long as sixth segment. The thoracic legs are conspicuously more slender than in the female. 

 Second pair have the seventh joint with claw longer than sixth joint; third and fourth pairs with the 

 spurs short and simple, while their seventh joint plus claw is only a little shorter than sixth 

 joint; on the three posterior pairs (fig. 3d) seventh joint together with its claw is much longer 



