404 



DE. r. LEUTHNER ON THE ODONTOLABINI. 



the resemblance of the mandibles of the priodont form to those of the female is only 

 accidental, and may be due to the disappearance of the gap in the middle of the man- 

 dibles (fig. G). The species of the genus Ileterochthes are among the most interesting 

 known to me, as the female mandibles are entirely differently formed, like an 

 amphiodont stage. 



The female of//, andamanensis (comp. accompanying woodcut, fig. 4. no. 9) has an 

 apical group of four or five contiguous teeth, and there are two anastomosing obtuse 

 teeth at the base ; these are separated by a gap from the apical teeth. There is a 

 slight projection on the upper side of the mandibles, just above the gap. 



1^-^ 



7 8 9 



Stages of development of mandibles in Heterochthes andamanensis. 

 No. 9, $ ; no. 8, smallest (J form, resembling ? ; nos. 4-6, mesodont forms ; nos. 1 and 2, telodont forms ; 



noa. 3 and 7, intermediate forms. 



The smallest male form (no. 8) stands at almost exactly the same stage as the female. 

 The mandibles exhibit an apical group of four or five teeth, divided by a gap from 

 the two obtuse basal teeth. On the upper side is a slight prominence, rather more 

 developed than in the female, and situated exactly over the middle of the gap. In the 

 next higher stage of the development of the mandibles (no. 7) the middle prominence 

 is more strongly marked, and more or less united with the basal teeth. In the third 

 form (no. 6) the central tooth is still more strongly developed. The basal teeth have 

 disappeared, and there are only two or three apical teeth (nos. 5, 4) instead of three 

 or four (mesodont form). When the mandibles are still larger (nos. 3, 2), the central 



