KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 21. N:0 5. 19 



The body is not keeled. The liead is more than twice as deep as long, provided on the 

 upper side with two divergent keels. The first pair of antennce are a little shorter than 

 half' the body. The first pair of pereiopoda with elongated carpi. The fifth jjair are as 

 long as, or a little shorter than, the sixth; the femur is spinously serrated along the 

 anterior and posterior margins, it is only a little shorter than the three foUowing joints 

 together; the apical spine-like process is slender, nearly straight, longer than the genu; the 

 tibia is much shorter than the carpus, the carjjus is almost six times longer than the 

 metacarpus. The seventh pair are as long as half the fifth. The last two ural segments 

 are coalesced. The uropoda are broad, minutely serrated; the inner margins of the first 

 pair are spinously serrated. The exteriör rami of the first and second pairs are very 

 minute, those of the third pair are very large, as long as the peduncle, and only a little 

 shorter than the inner rami. The inner rami of the last two pairs are much longer than 

 the pedunoles. The first pair do not reach beyond the others. The telson is triangulär, 

 a little longer than a third of the exteriör rami of the last pair. 



Colour. Ycllowish. 



Length. 8 — 10 mm., without rostrum o — 7,5 mm. 



Hilb. The North Atlantic. Lat. 62° N. Long. 15' W. (S. M.). 



Syn. 1885. Tyro (Jlausi, C. BOVALLIUS. "On sorae forgotteu genera among the Aniphipodous 



Crustacea». Bih. t. K. Sv. Vet. Ak. llandl. Bd. 10. 

 N:o 14, p. 14. 

 » » » 1887. »Arctic aud Aiitarctic Hy))erids». Vegn-Exp. Veteusk. 



Iakttagelser. Bd. 4, p. .5.52; pl. 40, fig. 1—3. 



Although Ty ro Clausi i.s \ery .similar to Tyro borealis in general habitus and in 

 the armature of" the fifth pair of pereiopoda and of the fir.st pair of uropoda, it is easily 

 distinguished fi"om that species as 'well as from its other congeners by the short fifth pair 

 of pereiopoda. 



The bodi/ is more narrowed than in Tyfo Sarsi, with a thinner and smoother 

 integument. 



The head (Pl. II, fig. 20) is very high with two divergent keels on the iipi)er side. 

 The lateral margins do not project into processes as in Tyro borealis. 



The eyes are small, round, and consist of 1.5 ocelli each. 



The Jirst pair of antennw (Pl. II, fig. 21) are feebly curved downwards. The 

 peduncle is one-jointed, tolerably thick, and equals a tenth of the lengtb of the flagellum. 

 The first joint of the flagellum is conical Avith three feebly marked keels, beset with long, 

 depressed, sharp-pointed, spine-like teeth. On the inner side of the joint there are trans- 

 verse rows of long haii's. The rest of the flagellum consists of only one join^^ which is 

 unusually long and narroAv, and equals about a sixth of the length of the first joint. 



The second pair of antennce consist in the female of a three-jointed, very short 

 rudiinentaiT piece; in the uiale they are similar to those of Tyro Sarsi. 



The pereion is evenly arched; the last three segments are as high as the preceding, not 

 longer than the third and fourth together. The fourth segment is the longest, the seventh 

 the shortest. 



