22 THÉEL, PRIAPULIDS AND SIPUNCULIDS OF THE SWEDISH ANTARCTIC EXPEDITION 1901 — 1903. 



pentagons, the number of lateral spines increases up to ten, but decreases again towards 

 the interiör of the gullet. 



From the above-given account of the dentary systems of the three forms of 

 Priapulus, it becomes evident that they are built after the same plan and present 

 the greatest resemblances, but that they, nevertheless, exhibit some constant differences. 



Fig 3. 



Fig. 4. 



Fig. 5. 



Fig. 2. Priapulus caudatus Lam. forma tuberculato-spinosus Laird. Diagram of tlic dentary apparatus. 

 I», dorsal side; V, ventral sidc; 1 — 6, the six pentagons of teeth; *, the pair of large tceth. 



Fig. 3. Priapulus bicaudatus Dan. Diagram of the dentary apparatus. D, dorsal side; V, ventral side; 

 1 — 5, the tive pentagons of teeth. 



Fig. 4. Ventral view of the posterior part of a male specimen of Priapulus caudatus Lam, from the 

 West-coast of Sweden: Ghillmar fjord, a, anal apcrture; rg, right genital pore; Ig, left genital pore. The median 

 space devoid of warts should be noticed. 



Fig. 5. Ventral view of the posterior part of a female specimen of Priapulus caudatus Lam. from Xpitz- 

 bergen: Ece fjord, a, anal apcrture; rg, right genital pore; Ig, left genital pore. The median space devoid of 

 warts should be noticed. 



When I was studying the aretie specimens of Priapulus caudatus in order to 

 comparc tliem with those from the antaretie region, my attention was attracted to 

 some remarkable arrangements in the organisation which are worthy of being men- 

 tioned. The annexed figures in the text explain satisfactorily the nature of these 

 arrangements, which ha ve hitherto, as faras I know, been almost entirely ignored. 



