20 ARKIV FÖR ZOOLOGI. BAND 2. N:0 8. 



sentially forwards; it has a rather considerable length, being 

 about as long as the length of the spirade, and its lower wall 

 is scarcely shorter than the iipjye?- one — in strong contra- 

 distinction to the above-described types. Seen from above 

 or below both latera] margins of the trunk are sinnafce and 

 besides diverging, so that its front end is nearly twice as broad 

 as the spirade. The lower wall of the trunk has a peculiarly 

 diitinized, obhque, triangulär area in its posteriorhalf (PL L, 

 fig. Ir); the base of this triangle is the front margin of the 

 spirade, while a narrow. diitinized band proceeds from the 

 vertex forwards and a little outwards to a point at the front 

 margin of the trunk near its exteriör angle. The area men- 

 tioned looks almost as if it consists of somewhat oblong or 

 eircular rings which are larger and more strongly chitinized 

 at the posterior margin of the area than in front ; the an- 

 terior margin of the spirade is t hus strongly diitinized. The 

 »lungs» are directed horizontally forwards and a little out- 

 wards; the margins of the pouches at their origin from the 

 bottom of the trunk are not perceptibly more chitinized than 

 their walls. 



It is an interesting fact that the Tartarides, which in 

 otlier respects are allied to Oxopoei in contradistinetion to 

 Amblypygi, in the structure of the respiratory organs deviate 

 very considerably from both groups in which these oi-gans are 

 rather similar. — That in Tartarides the respiratory organs 

 consist of a well developed, rather short tracheal trunk, from 

 the end of which a close row of compressed, not ramified tra- 

 cliese originate, can scarcely be denied. But the structure in 

 Tartarides is therefore an excellent starting-point for the 

 understanding of these organs in Scorpiones, Oxopoei, etc, 

 in which the trunk widens strongly upwards or even back- 

 wards, while its lower side is shorter or very much shorter 

 than the upper, or perhaps rather the posterior, wall, and the 

 terminal wall is very high; the result of the last-named feature 

 is that the respiratory »pouches» are much higher in all these 

 groups than in Tartarides, which is a type of small animals. 

 We think it worth adding that two circumstances show, 

 that in Pedipalpi each pair of »lungs» belongs to the segment 

 at the posterior margin of which their spirades are found, 

 viz., the respiratory organs are decidedly situated within this 



