12 Transactions of the Society. 



Nymph. 



The nympli of this species so closely resembles the perfect form 

 that I do not think any one would mistake it. I therefore have 

 not figured it, and only give here the differences from the perfect 

 form (beyond the ordinary one of being monodactyle instead of 

 tridactyle). 



The colour of the nymph is pure milky -vrhite, without a speck 

 of darker marking about it. 



The general thickness of the legs is greater in the nymph, and 

 the shapes of the respective joints are not so varied. 



The markings figured upon the cephalothoras of the adult are 

 not found on the nymph. 



The hairs bordering the abdomen are rather smaller in the 

 nymph than in the adult. 



The skin is covered with slight wrinkles or vermiform markings 

 instead of being polished. 



NOTASPIS LACUSTRIS, fl. Sp. PI. II. Fig. 6. 



Average length about • 5 mm. 

 „ breadth „ '33 „ 

 „ length of legs, Ist pair, about '26 mm. 

 4th „ „ -40 „ 



I have ventured to include this species in the genus Notaspis, 

 although this is a monodactyle species, and Nicolet defines the 

 genus as tridactyle ; but I have come to the conclusion that, 

 although it was perfectly natural for Nicolet, working from the 

 species he was acquainted with, to take the number of claws as dis- 

 tinctive of genus, yet there are some genera in which this cannot 

 be supported as a good characteristic. 



This species is strictly aquatic, but is not a swimming creature ; 

 indeed, none of the Orihatidse are. It crawls about the subaqueous 

 plants, and is confined to fresh water. It is often found covered 

 with diatomaceae, which adhere to it sufficiently tightly to be 

 preserved upon it. 



The colour is dull reddish-brown ; the texture is smooth but not 

 polished. 



The cephalothorax is less than half the length of the abdomen, 

 and forms a broad, short cone, with a slightly rounded apex ; it is 

 considerably rounded at the posterior angles. The base is almost 

 as wide as the anterior margin of the abdomen. There are not any 

 markings on the dorsal surfece, except two short ridges, which are 

 doubtless the homologues of the wings of a tectum, but otherwise 

 that part is absent. The stigmatic organs are not visible, and 

 there are not any interstigmatic hairs ; the rostral hairs are short 

 and curved. 



