442 BRITISH ORIBATII)^. 



The Lamellae are absent or quite rudimentary. 



The Tectopedia are scarcely indicated. 



The Apodemata are very strong and well marked, 

 and are joined to the sternum in all known species. 



The Opisthophragmatic processes are absent. 



The Legs are short, the fourth pair usually scarcely 

 passing the hind margin. They are thick and solid, 

 sometimes very much so (H. picea), and are generally 

 more or less regularly diminished in thickness from 

 the middle of the femur onward, when seen from 

 above. The coxae of the third pair are generally 

 nearly hemispherical and projecting; they may be 

 hidden under the abdomen {H. arrecta). The two 

 front pairs of femora are broad joints, rather flattened, 

 and generally with rather thin, short, proximal ends 

 turned almost at right angles. The genuals are longer 

 in proportion than in most genera, often as long as 

 the tibige. The tarsi are generally rather long, thick, 

 straight, and blunt-ended. The claws are monodactyle 

 in all species known at present. 



The Abdomen is usually a short ellipse, rounded 

 posteriorly, and generally rounded anteriorly, but 

 somewhat truncated in H. nanus and H. histriata, in 

 both of which species the shape of the abdomen is 

 longer. The uotogaster is always arched, generally 

 very strongly {H. picea, H. arrecta), and has not any 

 raised margin. This arching of the notogaster forms, 

 as above stated, the leading character of the genus. 



The Genital and Anal Plates are large ; the former 

 always square, the latter so in R. arrecta and H. nanus, 

 oblong in other British species. In H. nanus they are 

 distant from each other (from the long shape of the 

 abdomen) ; in H. arrecta they are much closer, but are 

 still separated (PI. XLTII, fig. 9) ; in H. picea, II. 

 nodosa, and H. histriata they are almost touching. 



The Tracheal system is most imperfectly developed 

 in this genus ; in N. arrecta I have succeeded in tracing 

 the small cephalotlioracic trachea, although they are 

 very small and delicate, but I failed to find any of the 



