EXTERNAL ANATOMY OF INSECTS. 599 



Cossyphus it stands out a little from the abdomen, so as 

 to form a kind of fence round it. Its shape generally ap- 

 proaches that of a scythe, being incurved and growing more 

 slender towards the apex a ; but it is sometimes straighter 

 and shorter. In Geotrupes and many other Lamelli- 

 corns, 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 Calandra Palmarum and many Cassidce 

 it slants to the scutellum ; in Chlamys it is sinuate, and 

 in Elater it has a deep cavity above the axis which re- 

 ceives the points of the phragma mentioned before 5 . 

 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 Nec?~ophorus 

 transversely, truncated ; in many Capricorns it is emar- 

 ginate ; in others, as Macropus longimanus, it is biden- 

 tate; in some Prioni, P. cinnamomeus, &c, it termi- 

 nates in a mucro at the internal angle ; and in Ceram- 

 byx Batus, horridus, &c, at the external; 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 Macruspis MacLeay, is obliquely trun- 

 cated to admit it, but where it is small it is generally rect- 

 angular, with the angle rounded ; in Buprestis vittata it 

 is obtusangular ; and in Dytiscus marginalise &c, it is 

 emarginate. In Cassida spinifex, perforata, &c, the hu- 

 meral 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 general it 



* Plate XXVIII. Fig. 8. h See above, p. 582. 



