1887.] 



ON CYCLESTHERIA HISLOPI. 



17 



its three first joints being produced above at the end to a somewhat 

 projecting process, bearing a number of strong recurved spines, 

 similar to those on the scape; whereas the three succeeding joints 

 are more simple, and have each only two spines above. The 

 terminal joint of this branch is a little longer than the preceding 

 joint and furnished with two slender spines at the upper edge 

 and two natatory setæ of equal size at the tip. The lower 

 branch is a little longer and also somewhat more slender than 

 the upper. with the joints but very slightly produced at the 

 end above and each having only two spines. The terminal joint 

 closely resembles that of the upper branch, with this exception, 

 however, that it has three natatory setæ at the tip. As to the 

 number of natatory setæ proceeding from the lower edge of each 

 branch. this would seem to be slightly variable. Generally, two 

 setæ are found on each joint, the outer of which is invariably 

 the larger, the inner being often very small, nay in some cases 

 altogether wanting in one or the other of the joints. The first joint 

 of the lower branch. however. exhibits in all specimens a somewhat 

 greater number of setæ, amounting from three to seven; and in 

 a few unusually large specimens I have found on some of the 

 other joints an additional seta behind the two others, making in 

 all three setæ, which increase successively in length toward the 

 end of the joints. All the setæ are distinctly biarticulate and 

 densely ciliated throughout the whole of their length. — The 

 antennæ are provided with numerous muscles, more or less filling 

 up the scape and also partly continued within the branches. Of 

 these muscles some are found issuing from the cuticle of the head 

 just above the base of the scape. Thus, on either side is seen 

 a rather strong muscle, consisting of 2 distinct bundles, (Pl. III, 

 fig. 5) immediately posterior to the eye, running between this 

 organ and the intestine to the anterior part of the base of 

 the scape. Another much stronger muscle, issuing close to the 

 insertion of the mandibles, enters the scape obliquely from behind. 

 and a third, rather slender, passes still more obliquely to the 

 scape. Within the latter part (see Pl. IV, fig. 1) are observed. 

 numerous muscles. that partly cross each other. some having 



Chr. Vid.-Selsk. Forh. 1887. Na 1. 2 



