1865.] 237 



marginal cell; the outer end of the discal cell emits four veins towards the 

 margin : the anterior among these veins is very arcuated at its basis, so that 

 the cell it frames in seems to be carved out of first posterior cell : great cross- 

 vein somewhat beyond the basis, but before the middle, of the discal cell ; fifth 

 longitudinal vein incurved at the tip. More structural details about this spe- 

 cies have been given among the generic characters. 



Hah. — White Mountains. N. EL, end of June. 1836 (nob.) ; two male 

 specimens. 



Observation. — I will mention here some peculiarities of the structure 

 of the thorax of this species, which 1 have omitted in its description, 

 as unimportant for its recognition. The thoracic transverse structure 

 is marked by a very delicate groove in the shape of a Y or of a fork, 

 the two ends of which run parallel towards the collare and the handle 

 reaches the scutellum ; a transverse impression on each side connects 

 this fork with the sides of the thorax, near the root of the wings and 

 thus completes the transverse suture. These slender grooves on the 

 thoracic dorsum foreshadow the more distinct sculpture of Triogma. 

 The scutellum in both genera has two distinct pits near its basis. 



The European C. distinctissima seems to be very like C. americana 

 in its coloring. 



Gen. X. TRIOGMA. 



Characters. — First longitudinal vein incurved at the tip towards the second 

 and ending in it (and not in the costa) ; one exterior marginal, a submarginal. 

 a discal and four posterior cells; the small cross-vein is often wanting, the sub- 

 marginal cell, near its basis, being in immediate contact with the discal cell. 

 Antennte 16-jointed ; joints short-oval or heart-shaped. Eyes bare, separated by 

 a rather broad interval above and below. Tibiae with distinct spurs at the tip. 

 Empodia distinct. Forceps of the male analogous to that of Cylindrotoma ; a 

 style or aculeus, three-lobed at the tip. is always jn-esent, often concealed, 

 sometimes projecting. The ovipositor of the female has short, broad valves, 

 obtuse at the tip. 



Head but moderately narrowed posteriorly and rather closely applied 

 to the collare. 



Proboscis very short ; jxtlpi of moderate length or rather short; last 

 joint elongated. 



The antennas, of the European T. trisulcata and the American T. 

 exsculpta have short-oval, almost rounded joints of the flagellum ; in 

 T. nodicornis the flagellum is moniliform, the joints being almost heart- 

 shaped and connected by short pedicels; the last joint of T. nodicornis 

 has a cylindrical prolongation which may be easily taken for a 17th- 

 joint ; the verticils are short. 



Co/lure moderately developed, in the shape of a transverse fold. 



The thorax of the three species at present known is sculptured in a 

 manner (juite unusual in the Tipularia and even among the Dvptera 



