396 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



p. 650) calls "Klauenteil" and "hyaline Platte." This has not been 

 drawn by anyone, but I have seen it in different species and shall 

 later present drawings. Behind this piece (or rather pair of pieces) 

 the sides of the head approach each other, leaving between them a 

 very narrow groove in which a structure called the gula is said to be 

 found (Prell, 1913) ; I have not been able to find this (see fig. 13). 

 The groove may be comparable to the ventral groove of Collembola, 

 though it does not continue on the thorax and its function is unknown. 

 Also the labium of Protura needs a thorough study, which was not 

 feasible at the time of this writing. 



Fig. 13. — Acerentomon doderoi Silv. Head, ventral. Labium dotted. Proximal 

 part of fulcrum and maxillae shown by dash lines. Presternum artificially with- 

 drawn from the head. 



