CRUSTACEA MALACOSTRACA. II. 27 



16. Pseudotanais Lilljeborgii G. O. Sars. 

 (PI. II, figs. 5 a— 5 g.) 



1881. Pseudotanais Lilljeborgii G. O. Sars, Arch, for Math, og Naturv. B. 7, p. 48. 

 ! 1897. Lilljeborgi Account Crust. Norw., Vol. II, p. 40; PI. XVII, fig. 2. 



Female. Sars has described and figured the female, while he has not seen any immature 

 or adult male. But his representation of the front end of the head with the eyes is not quite correct. 

 My fig. 5 a represents the outline of the carapace with the right antennula; it is seen that the cara- 

 pace is about two and a half times as broad as its front margin, which is transverse and a little 

 convex at the middle. Sars mentioned the eyes and figured thein as black spots, but while these 

 spots frequently are distinct in specimens preserved during some years in spirit, I was unable to find 

 them in specimens from several of the deeper "Ingolf" stations. Furthermore, internal visual elements 

 of an ocellus or some two to three ocelli seem sometimes but not always to be distinguishable, but I 

 have been unable to detect any cornea, so that the eyes must be considered quite rudimentary. 



The female is well distinguished from the other species by a combination of characters, among 

 which the most important may be enumerated. Third antennular joint is only slightly longer than 

 the second; the chela is from two and a half to three times as long as broad, not forcipate; the legs 

 are robust, the spurs of third to seventh pairs very broad and short or very short; the pleopods are 

 wanting, and the uropods are short, with the two-jointed exopod not quite as long as the proximal 

 joint of the rather stout endopod. — The length 1.55 — 2.05 mm . 



Immature Male. Agrees with the female excepting as to the abdomen, which is stronger 

 and proportionately somewhat or considerably longer than in that sex; furthermore the pleopods are 

 less or more developed according to age. In a younger male the pleopods are rather short with their 

 setse quite short. In a subadult specimen the pleopods are very well developed, conspicuously longer 

 than the uropods, with their rami very oblong and some of the setse longer than the rami. In the 

 last-named specimen the third antennular joint is a little thickened below; finally fig. 5g represents 

 the distal part of seventh leg, which agrees with that of the female in the following important parti- 

 culars: the spur (on fifth joint) is very short and broad; the seventh joint, which is somewhat thick, 

 is only one-third as long as sixth joint; the claw is thick and short. 



Adult Male. Somewhat similar to the male of P.forcipatus, but differs in several particulars. 

 In the relative length of the thoracic segments as compared with each other and in the strong 

 development of abdomen it agrees with the male of P. forcipaius and differs consequently much from 

 the female. 



The front margin of the head (fig. 5 b) between the outer angles of the antennular peduncles 

 is considerably convex; at the outer base of each antennula the lateral part of the head (fig. 5 c) is a 

 somewhat high, flatly rounded lobe which, seen from above (fig. 5b), is very conspicuous and marked 

 off by an oblique suture forming the continuation of the median part of the front margin; this antero- 

 lateral small part of the head is thus above, but not on the side, marked off as an eye-lobe, but a 

 real eye could not be discovered. — The seven-jointed antennulse (figs. 5 b and 5 c) are rather similar 

 to those of the male P. forcipaius, but the two proximal joints are less robust and the seventh joint 

 not longer than the sixth. 



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