78 Mr. J. O. Westwood on the 
XVII. On the Genus Mechidius of Mac Leay. By J.O. 
Westwoop, F.L.S., &c. 
[Read September, 1841.] 
Mazcuipwvs is one of those singular forms which disturb the pre- 
conceived arrangements of professed systematists, and of which 
New Holland affords such numberless examples. Mr. Kirby, who 
first described the insect, which served as the type of the genus, 
observed respecting it, that he could not clearly ascertain whether 
it belonged to Troa or Melolontha. He accordingly described it 
under the name of Trox spurius (Linn. Trans. xii. p. 462). Mr. 
W.S. Mac Leay subsequently proposed for it the generic name of 
Mechidius, considering it rather as nearer to 7’rox, and giving a 
detailed description of its oral structure, accompanied by outline 
figures of the essential parts from the pencil of Mr. Curtis (Hore 
Ent. i. p. 140, tab. 2, fig. 15). Since the publication of that 
work no addition has been made to our knowledge of the genus, 
and from the rarity of the insect, which does not appear to exist 
in any of the continental collections, but few Entomologists are 
acquainted with it, no figure of the entire insect having yet been 
published. 
Two species of this genus, recently added by the Rev. F. W. 
Hope to his collection, and a fourth in my own collection, have 
rendered necessary a more precise specific description of the typical 
species, whilst at the same time the opportunity of figuring so in- 
teresting a genus will, I am sure, be appreciated by the student. 
The parts of the mouth present several peculiarities of structure, 
which require a more detailed description than has been given of 
them. The clypeus has the lateral and anterior margins reflexed, 
the front being emarginate; beneath we perceive the part which 
Mr. Mac Leay terms the labrum, but which is certainly not arti- 
culated to the clypeus, although there is transverse impression, 
which seems to indicate that the clypeus and labrum are con- 
fluent. This supposed labrum is emarginate at its extremity, and 
meets the anterior margin of the mentum in order to close the 
mouth. The mandibles are horny, short, trigonate, the outer 
margin rounded, and the apex entire. On the side next the la- 
brum the mandibles are smooth and highly polished, but beneath 
they are furnished with two strong elevated ridges, forming an 
oblique canal, which causes them to appear furnished with two 
