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ROBERT S. BREED AND ELSIE F. BALL. 



I. The co-adaptation along the dorsal suture is shown in Figs. 

 10 and 1 1. The lower ridge d (Fig. 1 1) of the right elytron fits 

 into the groove c, the interlocking in this case being just the re- 

 verse of that found in Lacluwsterna (Fig. i). Moreover, there 

 is no clasp arrangement, the ridge c remaining as rigid as the 

 others. The suture would not hold together if there were not a 

 lateral stress exerted upon the elytra. In the anterior region, 



Fig. 10. Mid-dorsal region of a cross section of the elytra and metathorax of 

 Thymalits, showing the adaptation of the elytra to each other and to the metathoracic 

 groove. X 130- 



the ridges become very feeble and in the most anterior sections 

 (see Fig. 10) a ridge c on the left elytron fits into a groove / on 

 the right elytron thus reversing the condition found in the middle 

 and the posterior regions. 



d h 



Fin. II. Mid -dorsal region of a cross section of the elytra of Thytnahts in the 

 region immediately posterior to the metathorax. X '30- 



2. Fig. 10 shows in cross section the thickened edges of the 

 elytra, and the metathoracic groove {^g) into which they hook. 



