EXTERNAL ANATOMY OF INSECTS. 597 
as to form akind of fence round it. Its shape generally 
approaches that of a scythe, being incurved and growing 
more slender towards the apex’; but it is sometimes 
straighter and shorter. In Geotrupes and many other 
Lamellicorns, the base of the elytrum is nearly vertical, 
forming a right angle with the rest of it; it is usually 
transverse and straight; but in Cordylia Palmarum and 
many Casszde@ it slants to the scutellum; in Chlamys it is 
sinuate, and in Elater it has a deep cavity above the axis 
which receives the points of the phragma mentioned be- 
fore’. The apex of elytra is usually acute, the angle 
being formed by the confluence of a curving and straight 
line: but there are many exceptions; for instance, in 
Mylabris it is rounded ; in Hister obliquely, and in Ne- 
crophorus transversely, truncated ; in many Capricorns it 
is emarginate; in others, as Acrocinus longimanus, it is 
bidentate; in some Prionz, P. cinnamomeus, &c., it ter- 
minates in a mucro at the internal angle; and in Ceram- 
byx Batus, Oxyomus horridus K. MS., &c., at the exter- 
nal ; and, to name no more, in some species of Necydalis 
it ends in a long acumen. The scutellar angle in insects 
that have a large scutellum, as Macraspis, is obliquely 
truncated to admit it, but where it is small it is generally 
rectangular, with the angle rounded; in Bupreséis vit- 
tata it is obtusangular ; and in Dytiscus marginalis, &e., 
it is emarginate. In Casstda spinifer, perforata, &c., 
the humeral angle is producted into an acute lobe that 
stretches beyond the head, and in C. bicornis and Taurus 
it forms a horn at right angles with the elytrum. In 
Oxyomus it terminates in a spine or sharp point. In 
general it is either rectangular or rounded, with a pro- 
a Prate XXVIII. Fic. 8. » See above, p. 579. 
