BV .IAS. P. HILL. 41 



ol. Opening of lumen of notochord into the throat, p. Proboscis pore. 

 phc. Proboscis cavity, pc. Proboscis canal. ph>^. Periha^mal spaces, pps. 

 Peripharyngeal space. rf. Radial fibres passing between the outer and 

 fore walls of anterior rim of collar. r(. "Roots." sen. Subepidermic 

 capillary net of collar, slv. Median longitudinal vessel of the subepidermic 

 capillary net in the posterior ventral part of the collar, sn. " Synaptikel." 

 sp. Splanchnic epithelium of proboscis calom. sp7\ Septal prong of gill 

 skeleton, thh. Throat or mouth cavity, tpr. Tongue prongs of gill skeleton. 

 trc. Trunk coelom. vc-'i. Ventral collar septum. vgh. Ventral gonad 

 branches. v(js. Septal vessel, vn. Ventral nerve stem. ip. Ventral pro- 

 boscis pockets, vps. Ventral septum of proboscis. vv. Ventral vessel of 

 trunk, vir. Ventral wall of heart bladder. 



Ptychodera australiensis. 

 Plate I. 

 Fig. 1. — Enlarged dorsal view of a small preserved specimen. 

 Fig. 2. — Dorsal view of a portion of the abdominal region showing the two 



epidermal stripes. ( x 3. ) 

 Fig. 3. — Central part of a transverse section of the proboscis passing 



through the anterior free projection of the infolded ventral 



wall of the heart bladder. Zeiss A., oc. 1., cam. luc. 

 Fig. 4. — Transverse section slightly posterior to fig. 3, but from another 



series especially showing the infolding of the ventral heart 



bladder wall. Zeiss A., oc. 1., cam. luc. 



Plate II. 



Fig. 5. — Transverse section passing through about the middle region of 

 the proboscis organs. Zeiss A., oc. 1., cam. luc. 



Fig. 6. — Portion of glomerulus in transverse section. Zeiss D., oc. 1., 

 cam. luc. 



Fig. 7. — Transverse section of the splanchnic epithelium on the notochord. 

 Zeiss D., oc. 1., cam. luc. 



Plate III. 



Fig. 8. — Transverse section through the beginning of the proboscis neck. 

 Zeiss A., oc. 1., cam. luc. 



Fig. 9. — Transverse section of proboscis neck posterior to fig. 8 and pass- 

 ing through the ventral blind sac of the notochord. Zeiss A., 

 oc. 1., cam. luc. 



Fig. 10. — Transverse section of proboscis neck passing through the pro- 

 boscis canals and the connecting vessel between the efferent 

 proboscis vessels. Zeiss A., oc. 2., cam. luc. 



