334 EXTEROPXEUSTA FROM THE SOUTH PACIFIC, ETC. 



Fig. 61. Pt. biminiensis, n. sp. Dorsal view of anterior end, showing convergence and 

 overlapping of genital pleurae at anterior end of trunk. 



Fig. 62. Same. Section through body of stomochord in front of the pouched region, 

 showing wide cavity. 



Fig. 63. Same. Section through anterior portion of the coecal region of stomochord 

 in front of the pouches. 



Fig. 64. Same. Section through neck of proboscis in region of proboscis pores (see 

 Text). Between the right and left end-sacs is seen the anterior extremity of the right 

 perihaemal cavity, and below the right end-sac (left of figure) the solid posterior extremity 

 of pericardium. Xote dorso-lateral and ventrolateral pouches of stomochord (cf. PI. XXIX. 

 Fig. 17 a). Above the latter are seen the anterior rami of the cupule of nuchal skeleton. 



Fig. 65. Same. Portion of section behind region of insertion of proboscis into collar, 

 showing the post-trematic extension of the left end-sac, the anterior paired lumen of the 

 medullary cord with two separate medullary cavities, the process of skeletal substance enclosed 

 within the stomochord between the dorso-lateral pouches ; and the confluent ventral coelomic 

 canals (ventral coecum of proboscis cavity). 



Fig. 66. Pt. flava. Section through anterior collar-region of regenerating specimen shown 

 in PL XXVI. Fig. 5 A, to show formation of medullary tube by medullar}' folds. The section 

 cuts the anterior border of buccal orifice of stomochord tangentially. 



Fig. 67. Same. Similar section through middle of collar-region of same specimen as 

 preceding, showing appearance of medullary groove at this level. 



Fig. 68. Same. Portion of section through extreme anterior end of collar region of 

 regenerating individual shown in PI. XXYI. Fig. 5 B, to show the fusion of the medullary 

 folds over the medullary tube at this level. Posterior to this point the medullary canal is 

 still unclosed in this specimen. 



Fig. 69. Pt. rufieollis. Dorso-lateral portion of section through genital region of mature 

 female, to show the wide gaping of the genital duct. 



