ACARUS OF THE GENUS MYOBIA. 7 



smallest of all ; the claws are unequal, but there is a clear, chitinous, 

 curved, blunt-ended rod attached, larger than the ungues themselves. 

 The claws of the third leg (Figs. 8, 9), and of the fourth leg, are 

 slightly curved, unequal, didactyle, and considerably larger than 

 those of the second pair. 



The hairs on the ventral surface are spike-like, as in M. musculi. 



The Male (Fig. 2, under-side). 



Average length about 



„ greatest breadth about... 



„ length of legs, 1st pair about... 



ii ii ii ^na ,, ,, ... ... 



ii ii >i o^d pi ti "• 



ii ii n ^tn „ ,, ... ... 



„ ,, „ anal hairs ,, ... 



The male, it will be seen, is smaller than the female, but is of 

 much the same form, except that its legs and anal hairs are longer 

 in proportion ; it is therefore considerably narrower in shape than 

 the male of M. musculi, which is broader in proportion to its length 

 than the female, 



The whole of the above observations relative to the hairs of 

 the female, except those round the vulva, and as to the tarsi and 

 claws, will apply equally well to the male. 



The genital opening (Fig. 3) is placed on the anterior side of an 

 elevation far forward on the dorsal surface, being between the second 

 and third pairs of legs. It consists of a small aperture with slight 

 labia?, and is protected by a horse-shoe-shaped chitinous piece, not 

 unlike the sternite near the vulva of most Dermaldchi, but less 

 developed ; it is surrounded by several short spines. The penis 

 (Fig. 4) is an organ of remarkable size ; it is usually retracted 

 almost wholly into the abdomen, and then nearly touches the hind 

 margin, its point being directed forward ; it is a strong, hollowed 

 rod, of dark chitin, slightly curved, with the concavity upward, and 

 the rod is strongly bent upward near the tip, the actual tip being 

 again turned forward. At its posterior end it has attached to it a 

 somewhat elaborate framework of curved levers, the form of which 

 will be best understood by the drawing. It will be evident that 

 muscles pulling the posterior ends of these levers forward and down- 

 ward would produce the motion required for extrusion. 



As far as could be judged from the present experience, the numbers 

 of males and females appeared about equal. 



