WITH NOTES ON THE WEST INDIAN SPECIES. 



327 



PLATE XXVII. 



Fig. 6. Dorsal view of Pt. carnosa n. sp. to the end of the hepatic region ; abdominal 

 and caudal regions omitted. From preserved specimen, natural size. In front of the first 

 fracture the genital pleurae are united together across the middle line by a mucous junction. 



Fig. 6 A. Frontal view of the head of Pt. carnosa. There is a scar across the small 

 proboscis which probably indicates that the latter was recovering from an injury. The anterior 

 neuropore is indicated in the dorsal angle made by the junction of the proboscis and collar, 

 and below this are seen the lateral portions of the large buccal orifice. 



Fig. 7. Pt. rtificolUs, n. sp. The hepatic region is denoted by the diagonal markings 

 which commence shortly behind the termination of the genital ridges. The posterior end of 

 the body is represented in ventral view to show the transition from the abdominal to the 

 caudal region, x 2. 



Fig. 8. Spengelia porosa in lateral view. From a photograph (x about 2) taken by Mr G-rant 

 in the Physiological Laboratory at the University, Sydney, N.S.W. 



Fig. 8^. Sp. jjorosa. Ventral view of anterior end of macerated specimen showing the 

 cupule and keel of the nuchal skeleton ; the two horns of the glomerulus and the vermiform 

 process of the stomochord projecting into the proboscis. 



Fig. 9. Sp). alba, n. sp. The entire animal in three fragments ; the dotted lines show 

 where the fragments should join on to one another, x li. 



Fig. 9^. Sp. alba. Enlarged view of branchiogenital transition, x 6. 



Fig. 9 B. Sp>. alba. Enlarged view of genito-hepatic transition and portion of hepatic 

 region, to show smooth ventro-lateral epidermal tract. The dark line showing through in the 

 posterior pai't of the drawing is due to the lateral blood-vessel of the hepatic region. The 

 asterisk marks the corresponding points in Figs. 9 and 9 B. 



Fig. 9 C. Sj). alba. Ventral view of genito-hepatic transition to show the dilated ends 

 of the ventro-lateral epidermal tracts. 



PLATE XXVIII. 



Fig. 1 a. Pt. flava. Collar and anterior end of pharynx opened up by a ventral incision. 

 It shows the parabranchial ridges passing round into the epibranchial tract ; also the racemose 

 organ underlying the body of the nuchal skeleton immediately in front of the divaricating 

 cornua of the skeleton. The lobulation of the racemose organ varies greatly in extent, the 

 condition here represented being somewhat beyond the average. 



Fig. 1 b. Pt. carnosa. Similar view. Collar-flap projects far in front of insertion of 

 proboscis ; an epithelial pad underlies the nuchal skeleton in front of and below the point 

 of bifurcation (cf. PI. XXIX. Fig. 18). 



w. III. 4 5 



