526 Bulletin united states geological survey. 



about half an interspace's width from the outer margin ; beyond the sub- 

 median it is very faint, and 'above it the spot is broader; the third, 

 slightly narrower, subparallel to the second, but running more nearly at 

 right angles to the nervules, extends in a slightly sinuous course across 

 the median interspaces only, tapering apically. In addition to these 

 markings, there is a series of submarginal pale dots in the lower half of 

 the wing, one in the narrow (upper median) and two in each of the 

 broader interspaces, besides a larger roundish or subtransverse dark 

 spot, deepening centrally in color, in the medio-submedian interspace, 

 between the submarginal pale dots and the middle tongue of the large 

 pale spot, which here tend to inclose the dark spot in an annular pale 

 ring, and give it the appearance of a rather obscure ocellus. Above 

 the tail, the fringe Appears to be concolorous with the pale ground; 

 below it, darker than the adjoining dark ground-color. The scales on 

 the outer half of the front wing are two or three times as long as broad, 

 with straight parallel sides, a well-rounded base, and a deeply combed 

 apex, consisting of from three to five, usually four, entirely similar, equi- 

 distant, tapering, finely pointed teeth, of equal length, or the middle 

 ones slightly larger, the outer ones at the edges of the scale, all nearly 

 a third as long as the scale itself. 



Length of body 22™°^, of palpi 2.4n'«», last joint of same 1.3^% of anten- 

 nae 10.5'"'°, of club of same 2.5"^"^; breadth of latter 0.85™™, length of 

 thorax 6.5™™, its breadth 5.5™™; expanse of wings 54™™; length of front 

 wing 24.5™™, its outer margin 18™™, its inner margin 15™™; breadth of 

 wing, 14.5™™; length of hind wing, excluding tail, 18™™; additional 

 length of tail 3.25™™; breadth of latter at base 1™™, in the middle 0.55™™ j 

 greatest breadth of hind wing 16.75™™; length of abdomen 13™™; breadth 

 of same 5™™. 



DiPTERA: PALEMBOLUS ("diaj, ep.jSoXog). 



The dipterous family Sirmoneuridw, or Ifemestrinidce, is composed of 

 somewhat anomalous forms, allied to the Bombylidce, with which they 

 were formerly classed, but showing in the neuration of their wings a 

 decided affinity to the Wlidasidce. The family is divided by Loew inta 

 two sections, in one of which the mouth-parts are inconspicuous, while 

 in the other they project far beyond the head, and may even extend to 

 a length exceeding several times that of the body. It is a tropical 

 family, and only a single species {Rirmoneura clausa Sack, from Texas) 

 has been described from the United States, and only one more is known 

 from Korth America. The genus now brought to light from the Tertiary 

 rocks of Colorado is not only distinct from any previously known, but 

 belongs to the rhyucocephalous division of the family, now first recorded 

 from North America. 



The head is narrower than the thorax; the labium twice as long as 

 tbe thorax ; labrum and other aculiform parts of the proboscis a little 

 shorter, reaching as far as the base of the terminal knob of the probos- 



