XXtil. 



To these parts I have given the names, The Costa, The 

 Valmda, and The Sacculus (Them, pi. xlii.). 



THE COSTA. Pierce. 



The costa or upper margin of the whole valva is 

 generally thickened. It is occasionally decorated and may 

 take the form of a free arm (Xanthorhce montanata, pi. 

 xlv.) or of a free spatulate plate (Ortholitha bipunctaria, pi. 

 xlvii.), whilst it sometimes possesses a branching arm in 

 the middle, which I term The Costal Arm (Angerona 

 prunaria, pi. ix.). 



THE VALVULA. Pierce. 



The central part of the valva, lying between the costa 

 and the sacculus, I call The Valvula. It is in most cases 

 composed of thin semi-transparent chitine, and is covered 

 more or less with hair. As a rule the valvula is united to 

 the costa and sacculus, but sometimes it projects free. Its 

 outer margin is subject to extreme modification and ranges 

 from an even curve to a deeply emarginate one. 



THE SACCULUS. Pierce. 



The inner, or as drawn in the figures the lower, por- 

 tion of the valva has been called by me, in the "Noctuidae," 

 The Sacculus. This part invests the base of the valva and 

 is often extended on its outer margin into a free arm 

 (Asthena, pi. xxiv.). 



THE FURCA. Pierce. 



The two sacculi may project centrally quite apart from 

 the valvse and are sometimes fused together. To the organ 

 thus formed I have given the name of The Furca 

 (Ennomos autumnaria, pi. it?.). 



THE EIGHTH SEGMENT. 

 This segment bears no spiracles. The anal edge of 

 the sternite may be scalloped, and is often otherwise modi- 

 fied. Sometimes it is hardened and produced in a single, 



