Mr. G. Lewis on the Mouth-organs of two Rhysodidse. 483 



Three specimens (one male, two females) taken under a 

 log by Mr. G. F. Angas. 



Perhaps most nearly allied to Sp. nietanus and heteropygus 

 of de Saussure; but in these two species the anal valves are 

 not compressed. 



EXPLANATION OF PLATE XVI. 



a. Otostigma cormocephnlimtm, anterior extremity from above. 

 «'. Ditto, ditto, from below. 



«^. Ditto, posterior extremity from below. 



b. Scolopocryptops Meinerti, from above (nat. size). 

 61. Ditto, head from below. 



c. GeopMlus tenuitarsis, anterior extremity from above, 

 c'. Ditto, ditto, from below. 



c^. Ditto, posterior extremity from below, 

 c^. Ditto, posterior leg from the side. 



d. Strongylosoma semirugosum, 12th somite from above, 

 rf'. Ditto, anal somite from the side. 



d^. Ditto, copulatory foot. 



e. Spirostrejitus dominicanus, anterior extremity, 

 e'. l)itto, posterior extremity. 



f. Spiroholus dominiccs, anterior extremity, 

 yi. Ditto, posterior extremity. 



/^. Ditto, copulatory organ from before. 



f^. Ditto, ditto, from behind. 



f*. Ditto, ditto, from the side. 



y*. Ditto, ditto, central portion. 



f^. Ditto, ditto, central portion (apex). 



LXIII. — On the Mouth-organs of two Species q/Rhysodidae, 

 By George Lewis, F.L.S. 



By the kindness of the Rev. A. Matthews, who has dissected 

 and drawn them, I am able to give outlines of the mouth- 

 organs of Rhysodes niponensis, Lewis, and GUnidium vene- 

 fcum, Lewis, of which descriptions appeared in the July 

 number of this Magazine. Mr. Matthews found it exceed- 

 ingly difficult to make the dissections, owing to the hardness 

 of the chitiuous parts ; and it is solely due to Mr. Matthevvs's 

 persistent industry and a sacrifice of a good many specimens 

 that the results now given were obtained. Mr. Matthews 

 considers, he has been completely successful with the Cliai- 

 dium^ '"' although the dissection of the smallest Trichopteryx 

 would have been more easily accomplished, for the maxilla, 

 labium, &c. are exceedingly fragile, while the surrounding 

 integument is almost as hard as iron, and cannot be peneti-ated 

 without more or less danger to the finer parts ; '^ and he 

 also says : "The organs of the mouth are, without exception, 

 the most extraordinary I have ever seen : the labrum is very 

 small, the epistoma, or, rather, the clypeus and the meutum, 

 are very large and of the hardest and most impenetrable horn j 



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