l8o DISCOVERY REPORTS 



The anatomy of the genus Pneumodermopsis has been best described by Pruvot-Fol (1924). The 

 distinctive feature of the group is the presence of a membranous triangular outgrowth forming a 

 lateral gill on the right side, somewhat beyond the point of greatest diameter. There is no posterior 

 gill, and in some species— such as the present one— the posterior ciliated circle may persist long into 



Fig. 7. Pneumodermopsis paucidens. Outline drawings of a representative group of twelve specimens from station WS 996, 

 showing some of the variations of form encountered in preserved material. 



adult life. The hook-sacs are extremely small, forming a pair of short, blunt outgrowths at the sides 

 of the buccal mass, each containing a cluster of short chitinized hooks. The posterior (or median) lobe 

 of the foot is long, tapering and slender. The species represented here is clearly P. paucidens Boas. 

 Its chief distinguishing character is the number and arrangement of the suckers borne on the aceta- 

 buliferous appendages inserted on the dorsal wall of the buccal cavity. There is a long median arm 

 with a single large terminal sucker, more than twice the size of the lateral suckers, and much larger 

 indeed than might be deduced from the diagrammatic illustration of Tesch's key (1950). Two pairs 



