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



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

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

 half the body. The first pair of pereiopoda with elongated carpi. The fifth pair 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 following joints 

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

 tibia is much shorter than the carpus, the carpus 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 exterior 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 peduncles. The first pair do not reach beyond the others. The telson is triangular, 

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



Colour. Yellowish. 



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



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



Syu. 1885. Tyro Clausi, 0. BOVALL1US. »On some forgotten genera among the Amphipodous 



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

 N:o 14, p. 14. 

 » » » 1887. »Arctic and Antarctic Hyperids». Vega-Exp. Vetensk. 



lakttagelser. Bd. 4, p. 552; pi. 40, fig. 1—3. 



Although Tyro Clausi is very similar to Tyro borealis in general habitus and in 

 the armature of the fifth pair of pereiopoda and of the first pair of uropoda, it is easily 

 distinguished from that species as well as from its other congeners by the short fifth pair 

 of pereiopoda. 



The body is more narrowed than in Tyro Sarsi, with a thinner and smoother 

 integument. 



The head (PI. II, fig. 20) is very high Avith two divergent keels on the upper side. 

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



The eyes are small, round, and consist of 15 ocelli each. 



The first pair of antennce (PI. II, fig. 21) are feebly curved downwards. The 

 peduncle is one-jointed, tolerably thick, and equals a tenth of the length of the fiagellum. 

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

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

 verse rows of long hairs. The rest of the flagellum consists of only one joint, which is 

 unusually long and narrow, 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 

 rudimentary piece; in the male 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, 



