A Revision of the genus Tarucus. 271 



organ of special design, there is also a long horn-like 

 sclerite attached to each clasp arising from the same 

 point, or very near the same point as the special organ 

 just referred to, but developed in the opposite direction. 

 These sclerites appear to me to be capable of independent 

 movement; this, however, would not prevent combined 

 action with the other organ should occasion arise ; they 

 lie within the hollow of the clasps just above the lower 

 margins, and rise slightly upwards and forwards, often 

 extending beyond their (the clasps) apices. It is difficult 

 to believe that they can assist the clasps at all in gripping 

 the abdomen of the female, but they might easily drop 

 just below the abdomen and be useful as excitatory agents 

 by tapping each side of the lower area of the sternite; 

 they might well be called the " virgae excitatae." The 

 special organ referred to above can be termed the " tec- 

 torius " (used for a covering) ; it seems to me to be different 

 from the " anellus," being in no sense a cone-like tube, 

 nor anything like it ; it also quite differs from the " manica," 

 and is a distinct and peculiar development that I have not 

 hitherto met with. The " tectorius " rises from a point 

 in the very rear of the clasps, expanding immediately 

 hindwards {i. e. towards the abdomen) into two broad 

 chitinous curtains — one on each side — lying within the 

 cingulum ; these taper more or less rapidly in different 

 species and assume different contours. At the penal 

 aperture the anellus becomes apparent in the shape of a 

 solid ring, or, as in theophrastus, a loosely fitting tube 

 through which the aedoeagus passes ; this ring is soldered 

 on to the lateral curtains of the tectorius, which rises 

 slightly above the anellus, forming a small hood over it. 

 The whole organ is capable of considerable movement 

 fore and aft, and in the latter case can be moved right to 

 the back of the cingulum, in which case it takes with it 

 the aedoeagus, which is then thrown right out of its usual 

 horizontal position into a sharply angled one. It is most 

 probable that this organ (the tectorius) may be the per- 

 sistence of a very ancient character; it is very closely 

 similar to the cingulum or girdle, keeping the aedoeagus 

 strictly in position, and it appears to me to be a reasonable 

 proposition to consider it a reversion to the original 

 structure when there were two sets of armatures, one around 

 the anus and another protecting the sexual organs; or it 

 may be an instance of the survival of an atavic character. 



