ACARINA FROM THE JUAN FERNANDEZ ISLANDS 



60 1 



Shape broadly pyriform, the posterior margin being almost semicircular. 

 The dorsal side is very highly arched, the greatest height being almost equal 

 to the width and placed far backwards in the posterior half of the body from 

 where the surface slopes downwards backwards very steeply and forwards in 

 an even curve (figs. 101 — 103). 



The sides of the propodosoma are very sligthly concave and meet at an 

 angle of 90 degrees. 



Propodosoma so completely fused with the hysterosoma that not even 

 a trace of the suture is seen. No traces of lamellae are to be seen on the 

 dorsal side of the propodosoma but at the sides in the posterior half there are 

 horizontal blades, which are triangular in outline, tapering gradually forwards. 



Are these structures really to be interpreted as true lamellae, although 

 their position is so different from the typical one? OUDEMANS who discusses 

 this question (1917, p. 4 — 5) holds the view that they are and finds support 



101 102 103 



Figs. loi — 103. Galumna pacifica n. sp. 

 loi. Lateral view. 102. Dorsal view. 103. Ventral view. 



for this in the fact that their anterior ends are shaped as small but distinct 

 cusps. 



In the present species, however, there are no such cusps nor are the 

 hairs homologuous to the lamellar hairs inserted near the anterior ends of the 

 »pseudolamellae». On dissecting the rostrum we find that the lamellae continue 

 as low but sharp ridges bent downwards in an even curve along the sides of 

 the propodosoma (fig. 104). 



The interlamellar and lamellar hairs are very small and inconspicuous 

 (fig. 104), as are also the rostral hairs. The latter are inserted in the middle 

 of a thin blade, forming the anterior edge of the rostrum and their pores con- 

 tinue as narrow canals to the base of the rim exactly as is the case in some 

 Uropodidae, where the edges of the body also form thin blades. 



In the middle of the anterior edge of the rostrum there is a sharp tooth 

 in front of which there is a square depression. 



The structure recalls vividly that described by Sellnick (1925, p. 81, 

 fig. 3) on Stictozetes^x) medialis, and it may be that it is a not uncommon 

 feature amongst the Galumninae, although hitherto overlooked. 



Behind the thin plate the rostrum is finally transversally striated. 



The pseudostigmata (fig. 105) are almost hidden underneath the base 



