88 PROF. W. J. DAKIN" ON A NEW SPECIES OF 



was never more than twice the width of the collar. In the preserved 

 specimens the length o£ the proboscis varies from 2'5 mm. to 4 mm. 



Collar. 



In both the living and the preserved specimens the surface of the collar 

 can be subdivided into five characteristic regions, as in other species of 

 Ptycliodera. The most anterior of these regions occupies a little more than 

 half the collar. In front it possesses a crinkled margin, surrounding the 

 narrow neck or base of the proboscis. The diameter of the collar diminishes 

 slightly towards the end of this anterior region, and ultimately we reach the 

 second region — a circular groove, — which, as we shall see later, is also well- 

 marked histologically. This groove is succeeded by a circular cushion, 

 behind which is a deep furrow in which the epithelium forms a smaller 

 cushion. Lastly, we come to the fifth region, which forms the posterior 

 maroin of the collar. 



The total length of the collar in the preserved specimens, in which the 

 proboscis was from 2*5-4 mm. in length, varied from 2"3-4 mm. That is to 

 say, the collar and proboscis, in the contracted state, are almost equal in 

 length. 



Trunh. 



Branchio genital Region. — This region is characterised by the possession of 

 genital pleura, which are attached anteriorly to the collar (PI. 10. fig. 1). 

 These genital wings are slightly different from those of Pt. flava in their 

 point of origin. They do not arise quite so far ventrally, and in no case 

 is there such an exposed branchial region of the alimentary canal as that 

 figured by Willey for Pt. flava *. 



The genital pleura do not overlap, nor are they infolded. For the greater 

 part their edges are just in contact in the median line. They remain for 

 some distance constant in size, for a distance approximately equal to the 

 combined lengths of the proboscis and collar. The wings are, in fact, just 

 as large where they adjoin the collar as at any other point in this region of 

 greatest development. A few millimetres in front of the anterior hepatic 

 cseca the pleura commence to decrease in size. This decrease is, however, 

 very gradual, and thus the pleura overlap the most anterior hepatic cseca. 

 Finally, nothing is left of the genital wings but two ridges, which can be 

 traced posteriorly for some distance at the sides of the hepatic cseca. 



The Reproductive Organs occur in the pleura. 



The length of the branchiogenital region is approximately 6-7 mm. 



Hepatic Region. — The length of the hepatic region is about 15 mm. The 

 saccules occur as paired elevations separated by a groove, the larger ones 

 being lobulated. Their greatest development is just a little distance behind 



* Willey, 'Zoological Results, based on Material' etc. part iii. 1899, plate 26. 



