1919] Essenberg: The Pteropod Desmopterus Pacificus (Sp. nov.) 87 



Comparison 



Desmopterus pacificus greatly resembles in general appearance 

 Desmopterus papilio, but differs sharply from the latter in some char- 

 acteristics. The most striking difference is in the size and the shape 

 of the epipodial tentacles (fig. 1 ) . In Desmopterus papilio the tentacles 

 are long, far exceeding the length of the wings and extending behind 

 as two whip-like organs, sometimes coiled. They are broader at tin- 

 base and decrease slightly in width toward the distal extremities. They 

 are covered with cilia. In Desmopterus pacificus the epipodial tentacles 

 are spade-shaped and short, their length being less than that of the 



Fig. 2. Ventral view of Desmopterus pacificus. X 100. Drawn from life. 



protruding lobes of the wings. They are covered with cilia and rough 

 elevations (fig. 2). The head of D. papilio is bent more abruptly than 

 that of D. pacificus. The wings of the former are also proportionally 

 longer than are those of the latter (figs. 1 and 2). 



Behavior. 



A few observations on the behavior of Desmopterus pacificus have 

 been possible. The animal is graceful in its locomotion, and with its 

 large wings and bright red color spots scattered in patches over the 

 body and wings, it resembles more a butterfly than a mollusc. In 

 locomotion D. pacificus uses its wings very much in the same manner 

 as any broad-winged animal Hying in the air. With a sudden, jerky 

 movement of tin' wings the pteropod sets the body in motion and then 



