NATURAL SCIENCES OP PHILADELPHIA. 255 



1 have been able to see it distinctly in Arrhenica s p i n o s a : it is figured and 

 described below. 



My chief attention has been directed to the structure of the external forceps 

 for the purpose of classification; everything remains to be done, as yet, in the 

 study of the more complicated and delicate internal organs. In the descrip- 

 tion of the figures which follows, I simply relate what I have seen, without 

 attempting any generalization. 



Fig. 1, forceps of L. d e f u n c t a from below. 



Fig. 2, the same, from above ; aa, soft, fleshy lobes ; 66, horny, falciform ap- 

 pendages, moveable with the lobes, and closely applied although not attached to 

 them ; they are fastened only by the base ; cc, horny, projecting points of the 

 internal organs. 



Fig. 3, forceps of Dicranomyia humidicola from above ; aa and bb as in 

 fig. 2 ; dd, horny, square appendages, bearing each a pair of bristles ; e, point 

 of the anal style, visible between the two lobes. 



Fig. 4, forceps of Dicranomyia 1 i b e r t a from above ; aa and bb, like in fig. 



2 ; dd, horny, rostriform appendages, with bristles ; e, anal style. 



Fig. 4a, anal style of D. 1 i b e r t a, seen from below. 



Fig. 5, one-half of the forceps of Dicranomyia gladiator from above; a 

 and b, as in fig. 2 ; e, anal style. 



Fig. 6, forceps of Limnobia solitaria from above, half closed; aa, move- 

 able, coriaceous halves, with appendages (66) ; these appendages consist of two 

 lamels, which are closely applied to each other and never divergent; the out- 

 side lamel is horny ; the inside one seems to be coriaceous ; e, is the anal style , 

 cc, projecting internal organs ; ff, are soft eminences, (perhaps rudiments of the 

 large soft lobes of Dicranomyia?) 



Fig. 7, represents the forceps of Limnobia indigena from above; the 

 lamels bb are also double; in some species, as inL. tristigma, I could not 

 distinguish whether the lamels were double. 



Fig. 8, forceps of Rhipidia domestica from above, and open; aa, 66, cc, 

 dd and e, as in the preceding figures. 



Fig. 9, the same forceps, from below and closed ; e, anal style. 



Fig. 10, forceps of Teucholabis complexa from above; 10a, one-half of 

 the same, from below ; aa and bb, horny appendages. 



Fig. 11, forceps of Antocha saxicola from above; aa, double appendages, 

 consisting of a horny and a soft point, closely joined. 



Fig. 12, half of the forceps of Elephantomyia canadensis from below 

 aa, horny appendages. 



Fig. 12a, forceps of Dicranoptycha ni gripes from above; y, are short 

 black bristles ; xx, indistinct, horny appendages. In this species I had for the 

 first time a glimpse of the structure of the slender, horny, hook-shaped organ, 

 figured farther below (fig. 276), but occurring in most species. When D. 

 ni gripes opens the forceps this hook comes into a sort of erection and 

 spreads outside of the forceps in the shape of fig. 12, 6; aa, are slender and 

 horny ; 66, is a small forceps, moving independently of aa } and opening or 

 closing at the point c. 



Fig. 13, one-half of the forceps of D. s o b r i n a. 



Fig. 14, forceps of Cryptolabis paradoxa from above ; 14 a, the same from 

 below ; aa, are horny appendages ; they are small and indistinct, being closely 

 applied to the fleshy part of the forceps ; 6, seems to be the rudiment of an 

 anal style. 



Fig. 15, tip of the abdomen of Cryptolabis paradoxa, female, from the 

 side ; fig. 15a, the same, from above ; there are no visible horny lamels ; tb* 

 tips, aa, are beset with microscopic bristles. 



Fig. 16, forceps of Gonomyia b la nda from above and open. 



Fig. 17, half of the forceps of Gonomyia cognatella, from above. 



1859.] 



