ACARINA FROM THE JUAN FERNANDEZ ISLANDS 567 



been able to ascertain that the articulation of its legs is typical and that the 

 claws are sessil. 



But, on the other hand, the maxillae of Plateremceus are built essentially 

 on the same plan as those of Neoliodes, as I have pointed out above. 



The structure of the legs is, however, so unique in PlateremcBus that the 

 raising of it to the type of a family is certainly justified. This family is as 

 yet rather isolated but is related to the Neolididce. 



Platereiiiaeidae nov. fam. 



Diagnosis: Hysterosoma flat, covered by 4 concentrical skins (i 

 larval, 3 nymphal exuviae). Body and legs covered by a thick layer 

 of secretion. Terminal ends of femur, genu and tibia narrow, arti- 

 culating in sockets of resp. genu, tibia and tarsus. Claws three, on 

 top of small peduncle. 



Typical genus: Plateremcetis (Berl.) TragArdh. 



4. Platerenieus vestitus n. sp. — Figs. 20 — 31. 



Length 880 [x, width 600 m. Length of propodosoma 250 [i, width 250 [t. 

 Length of hysterosoma 625 [t. 



Colour bright red-brown. Texture beautifully areolated through minute, 

 circular depressions (fig. 22). The cover of secretion is thick (fig. 24) and of 

 a spongy texture; it seems to be composed of perpendicular cylindrical pieces 

 of waxy matter packed densely together; the surface is irregularly reticulated. 



Propodosoma (fig. 20) as long as it is wide at the base, rounded at the 

 top. There are no lamellae nor any true ridges but half-way between coxa I 

 and the top the surface slopes abruptly downwards; in front of this the cir- 

 cular depressions are much smaller than further backwards. The posterior part 

 behind the acetabula I is also depressed so that the median third of the propodo- 

 soma forms a very broad transversal ridge. At the posterolateral angles of 

 this ridge, at the foot of the slope there is a sharp tooth directed obliquely 

 backwards and outwards which is opposed to a similar tooth which points in 

 the opposite direction (fig. 25). This structure vividly recalls the teeth found 

 in Odontocepheus on both sides of the suture between propodo- and hysterosoma. 

 Presumably in both instances they add to the rigidity of the cuticle. The 

 interlamellar hairs are placed on a level with the pseudostigmata and close to 

 them and are very short but stout and almost perpendicular. I have not 

 been able to find any interlamellar hairs but marginally, near the top of the 

 rostrum there is a pair of rather short hairs curved inwards, which may either 

 be homologuous to these hairs, in which case the rostral hairs have dis- 

 appeared, or are true rostral hairs. 



The pseudostigma (fig. 25) is of a rather peculiar shape; from a 

 narrow circular base it widens to twice is basal diameter and is bent obliquely 

 downwards, outwards and forwards; the posterolateral angle is flattened to a 

 blade and the anteromedian angle has the same shape, but is smaller. The 



