24 THÉEL, PRIAPULIDS AND SIPUNCULIDS OF THE SWEDISII ANTARCTIC EXPEDITION 1901 — 1903. 



Now, it is remarkable that the position of the anal aperture should not be 

 confined to a fixed place; for in 6 specimens examined it had its place on the right 

 side of the genital pores, and in 10 specimens it was situated on the left side of them. 



Considering that all the sex specimes first examined, had the anus on the right 

 side and were males, and that seven of the remaining ones had the anus on the left 

 side and were females, I thought at first that I had come a cross a case of sexual 

 dimorphism. But this supposition did not hold good, since I found that three spe- 

 cimens were males, though they had the anus on the left side. 



With regard to other conditions in the organisation of Priapiäus caudatus which, 

 to my mind, have been almost ignored, I refer the reader to the figures 6 — 8 in text 

 and to the explanations of them. 



Priapulus horridus n. 



Pl. II. figs. 13—19. 



Introvert about a fourih of the total body-length, provided with small spar se conical 

 papillce arranged in 25 longitudinal rows. Trunk glassy, transparent, anniäaled, with 

 about 29 or 30 distinctly marked rings. Caudal appendage, slightly longer than a fourih 

 of the total animal, divided by circular incisions into four segments, the terminal one 

 being most voluminous, covered with powerful spines and carrying anteriorly remains of 

 small respiratory bladders. Mouih with chitinous teeth. 



Total length of the animal about G mm.; introvert = 1,3 mm.; trunk = 2.r> mm.; 

 caudal appendage = 1.9 mm. 



Habitat. — Coast of Uruguay, 33° 0' s.— 51° 10' w., 80 m., blackish grey clay. 

 Swedish South-Polar Expedition, 12 /i2 1901. — A single specimen. 



Considering that only a single specimen of minute dimensions has been at my 

 disposal for examination, the diagnosis and the description must needs be very 

 deficient. 



The introvert deviates conspicuously from that of other Priapulids. Its pa- 

 pillse are diminutive and sparse, which results in the disposition of them in 25 longi- 

 tudinal rows being somewhat obscure, this being the case especially in the posterior 

 half of the introvert, where it is almost devoid of papillse. Owing to this property 

 the species assumes a somewhat stränge appearance. For, in the other known species 

 the papillse are rather large and lie close together, forming 25 very distinct longi- 

 tudinal rows all along the introvert (figs. 13 and 14). 



The skin of the tkunk is glassy and transparent, the alimentary canal, the 

 retractor muscles and the reproductive organs being discernible through it. It pre- 

 sents 29 or 30 rings, which are sharply marked by rather deep incisions between 

 them. Posteriorly, the trunk is characterized by a circular ridgc and by its body- 

 wall being bent inwards towards that place where the caudal-appendage takes its 

 origin, thus presenting an almust truncate aspect. 



The girdle of warts round the posterior extremity of the trunk — so charac- 

 teristic of the forms of Priapulus caudatus - - seems to be absent, or possibly they 



