ACARIDA 



(ORIBATIDAE) 



A. D. MICHAEL 



F. L. S. - F. Z. S. — F. R. M. S. — etc. 



INTRODUCTION 



The collection contains very numerous spécimens but only three species, ail belonging 

 to the genus Notaspis ; of thèse one is represented only by a single very much injured spécimen, 

 far too imperfect to allow of its being identified or described, it is a very minute créature. 

 The other two species are amply represented by a large séries of spécimens in ail stages. 

 They are certainly distinct species, but are closely allied and hâve considérable resemblance 

 to each other ; much more than either has to any species hitherto known. Ail the species 

 are terrestrial and were found in moss and lichen on the Antarctic lands, in the de Gerlache 

 strait, between South latitudes 64 23' and 67 5ç/ and West longitudes 62 02' and 70 3g'. 

 The nearest allies amongst recorded species are probably Notaspis lucorum and N. oblonga, 

 both lichen-eating Acari. 



The two species hère described are interesting because they shew some external diffé- 

 rences between the sexes ; although thèse différences are slight yet they enable an acarologist 

 to separate the sexes, whereas external sexual dimorphism is hitherto practically unknown in 

 the Oribatidae. I ascertained for certain that the dimorphism is really sexual by dissecting 

 out the internai génital organs of both sexes. 



Family Oribatidae 



Notaspis antarctica sp. n. 



Average length, about i mm ,o5 \ Thèse measurements are taken from the 9, those 



Average breadth, about o mm ,78 ' of the c? are about 6 to 7 per cent less. 



Form pyriform, rounded posteriorlv. 



Color dark chestnut-brown (castaneus), almost black, with a metallic lustre. 



Texture dull and roughish, rather finely granular ; granulations about i5o to the 

 linear m. m. on the abdomen, where they are most distinct. The céphalothorax and legs are 

 fully chitinized, but the abdomen, although it has the appearance of being so, readily collapses 



