REPORT ON THE PTEROPODA. 17 



are very small and placed on long and thick peduncles, the anterior (distal) pair being- 

 inserted at the same height as the large median sucker. 



Radula. — Formula 6:1:6; median tooth tricuspid. 



Hook-sacs. — Depressions containing from forty to fifty hooks. 



Colour. — Brownish. 



Length, 4"5 mm. The two posterior ciliated rings remain until a late period. 



Habitat. — South-East Pacific, off Caldera (Chili), about lat. 27° S. ; " Vettor Pisani" 

 Expedition, February 18, 1883. 



4. Dexiobranchasa paucidens, Boas. 1 



1886. Dexiobranchasa paucidens, Boas, Spolia atlantica, K. dansk. Vidensk. Selsk. Skriv., 6 



Raekke, Bd. iv. p. 160, pi. vii. figs. 105, 106. 



Foot. — Posterior lobe rather short. 



Lateral Gill very short. 



Buccal Appendages. — The suckers corresponding to the lateral appendages are 

 inserted on the ventral wall of the buccal cavity, by very short peduncles, from eleven to 

 thirteen in number; they are not arranged in two distinct groups, but are placed in a 

 single row, forming a continuous semicircle. The median appendage is well developed ; 

 its four lateral suckers are larger than those corresponding to the lateral appendages, and 

 are set on long and thick peduncles ; the terminal sucker is larger than these four. 



Radula. — Formula 2:1:2; the median tooth is bicuspid. 



Hook-sacs. — Each rudiment of a hook-sac bears from four to six very short, thick, and 

 slightly bent hooks. 



Length, 5 mm. 



Habitat. — Atlantic Ocean, on the route from Brazil to Europe (Copenhagen Museum). 



*5. Dexiobranchasa polycotyla, Boas (PI. I. figs. 4, 5). 



1886. Dexiobranchasa polycotyla, Boas, Spolia atlantica, K. dansk. Vidensk. Selsk. Skriv., 6 



Raekke, Bd. iv. p. 161. 



Foot. — Posterior lobe long. 



Lateral Gill long. 



Buccal Appendages. — The suckers corresponding to the lateral appendages are 

 arranged alternately in two rows, and form two distinct groups (right and left), each 

 including from ten to twelve suckers with very short peduncles. Median appendage 

 well developed, bearing a terminal sucker larger than those of the lateral groups ; the four 

 lateral suckers of the median appendage are nearly of the same size as these last. 



1 I have not been ahle to examine this species ; the following characters are compiled from Boas' description and 

 figures. 



(zool. chall. exp. — part Lvin. — 1887.) Mmm 3 



