1919] Deltometopus Rufipes Melts 51 



Mesad of these are a group of structures which seem to be 

 maxillae and labium but these can only be seen distinctly under 

 the oil immersion lens. The median portion, which is pointed at 

 the end (Figs. 3 and 8, lb) has a longer, sharp projection on 

 either side which appears to be two-segmented. The dorsal 

 surface of this structure (Fig. 8) shows a long tube connected 

 with the median projection which I have traced back into the 

 prothorax and may be the alimentary canal, although it is very 

 small and the salivary duct should open here. The tube seems 

 to have a chitinous lining, however. Laterad of these structures 

 and slightly dorsad of them are what appear to be maxillae. 

 The distal end bears a cluster of projections which appear to be 

 arranged in a circle. These structures are only a little less 

 strongly chitinized than the mandibles. There has been so little 

 morphological work done on this type of head that one is rather 

 at a loss to account for their peculiar structure and extremely 

 doubtful as to the homology of parts. 



The entire surface of the thorax and abdomen is very finely 

 striate, except when otherwise indicated, and all the body seg- 

 ments are very similar, except that the thoracic segments are 

 shorter in proportion to their width. than those of the abdomen. 

 There are no traces of legs or prolegs. Each segment except the 

 caudal one has some very distinct areas which appear velvety 

 under a low power lens as if densely covered with fine setae. 

 On the dorsal surface of the prothorax this area is triangular and 

 located near the caudal part of the segment but on the other 

 thoracic segments it is cephalic and somewhat triradiate. The 

 areas are ovate on the abdominal segments and located near the 

 cephalic margin. The areas are the same shape on the ventral 

 surface except that the median projection is lacking on the 

 m.esothorax and metathorax. These areas are really covered 

 with scales as shown much enlarged in Fig. 11, and a few fine 

 setae are also present. Caudad of these velvety areas on the 

 mesothorax and metathorax, on both surfaces, are much coarser 

 striations than on the remainder of the segment. Near the 

 caudal margin of each body segment except the prothorax and 

 the last abdominal segment on both surfaces, and the eighth 

 segment on the dorsal surface, is a clear, smooth area clearly 

 outlined by a fine, slightly elevated, brown, chitinous ring. 

 These are almost semicircular in outline on all segments except 

 the ventral surface of the eighth abdominal, where it is much 



