394 Mr. F. Smith’s Deseriptions 
margin of the thorax, a minute spot in the middle of the mesothorax, 
the inner margin of the tegula, the posterior margin of the scu- 
tellum, and a large ovate spot on each side of the metathorax, 
yellow; a subtriangular spot beneath the wings, and the legs 
beneath, yellow ; a yellow spot on the intermediate and posterior 
coxe, all the trochanters, the base of the anterior and interme- 
diate coxe, as well as the anterior tibia, black; the wings sub- 
hyaline, the nervures black; a broad yellow fascia, slightly inter- 
rupted in the middle, on the margin of the basal segment of the 
abdomen ; the three following segments have each a narrower 
interrupted fascia; on the apical margin of the fifth segment an’ 
entire fascia, emarginate in the middle; beneath yellow, the second 
segment having a transverse black spot at its basal margin, and 
the three following having each a narrow central black stripe at 
the basal margin; the sixth segment black, with the tip more or 
less yellow. 
Hab. Swan River. 
Fam. APID #&, Leach. 
Genus THauMATOSoMA, n. g. 
Labial palpi four-jointed, the two basal joints elongate, their 
length about equal, the third and fourth joints minute and sub- 
clavate, inserted at the apex of the second joint; the labial palpi 
and the labium of equal length. The maxillary palpi two-jointed, 
minute; the basal joint short, stout and cylindric, the second 
about the same length as the first, but much more slender and 
pointed at the apex. The basal lobe of the maxille shorter than 
the apical one, which is elongate, lanceolate and curved. Head 
as wide as the thorax; eyes large, lateral and elongate-ovate ; 
the ocelli three in a triangle on the vertex, the posterior pair 
placed in a line with the posterior margin of the eyes ; the labrum 
elongate, produced and rounded anteriorly; the antenne capitate 
(in the male), elongate, reaching to the middle of the abdomen, 
the club compound, formed of the two apical joints compressed 
and pyriform. ‘The anterior wings have one marginal and two 
submarginal cells, the latter receiving both the recurrent ner- 
vures, the first near the basal, the second near the apical angle of 
the cell. ‘The legs simple. Abdomen oblong, the sides parallel, 
rounded at the base and apex. 
It will be seen that the above characters, with the exception of 
the capitate antenna, are those of the genus Megachile ; but the 
exceptional character is so remarkable when possessed by a mem- 
ber of the great family Apid@, that I have thought it desirable to 
depart from the rigid observance of those Jaws which usually 
