GENUS HYPOCTHONIUS. 533 



back. The lateral edges of the abdomen are provided 

 with thin blades in most species, which may be 

 large and conspicuous as in H. rufnlns, where they are 

 formed by the depression of the dorsal surface (fig. 6), 

 less conspicuous as in H. palUduluSi where they are 

 formed by the thinning of the ventral surface, or 

 almost obsolete as in H. lanatuSy where they are formed 

 in the same way and confined to the anterior parts of 

 the abdomen. These blades have but little analogy to 

 the pteromorphse of the Pterogasterina. 



The Genital and Anal Plates are much of the same 

 type as is most common in Nothrus, viz. large and close 

 together, the former being the broader ; in Hypodho- 

 nius the genital plates are sometimes far the larger, so 

 as to admit of the passage of the egg, which is of 

 remarkable size. 



The Ventral Plate is small and more or less 

 triangular, the dorsal plate being much sufflexed on to 

 the ventral side. 



I have not had much opportunity of examining the 

 internal anatomy of this genus, but I may mention that 

 in the species known to me the ovipositor seems short 

 and thick, and only one egg appears to ripen at a 

 time, but this ovum is remarkably large. 



The Hairs attain a singular development in some 

 species, the long serrated spines on the notogaster of 

 H. lanatus, and the woolly hairs on other parts of its 

 body, are the best examples ; but the hairs on the noto- 

 gaster of If. rufulus are also somewhat exceptional. 



The Nymphs of this genus usually resemble the 

 adults but are lighter in colour. 



The Habitats appear to be chiefly moss growing on 

 the ground in damp woods, comparatively dry sphag- 

 num, not that in water, and occasionally old cellars, &c. 



