404 DR. F. 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. 6). The species of the genus Heterochthes are among the most interesting 
known to me, as the female mandibles are entirely differently formed, like an 
amphiodont stage. 
The female of 1. 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. 
Fig. 4. 
Stages of development of mandibles in Heterochthes andamanensis. 
No. 9, 2; no. 8, smallest ¢ form, resembling 2; nos. 4-6, mesodont forms; nos. 1 and 2, telodont forms; 
nos. 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 
