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PROCEEDINGS OF THE NATIONAL MUSEUM 



space is, in D. curtus, strongly suggestive of the members of the 1-3-2 

 group except that there is no indication of segmentation between the 

 proximahnost seta and the other three. 



Along the inner lateral surface of the two distal exopodite segments 

 of the 1-3-2 group are fom- plumose setae, one on the inner-distal 

 lateral surface of the second segment and three on the lateral sm-face 

 of the third. In addition, the proximal lateral margin of the third 

 segment is plumose. Although both of the species in the 1-2-2 

 group, D. curtus and D. litus, have four plumose setae along the second 

 or distal exopodite segment, there is no indication of a plumose 

 sm'face between the first or proximalmost seta and the second. The 

 spinelike process projecting inward from the inner surface of the 

 first exopodite segment is distinctly separated from the segment by 

 a line of division in all of the species except D. hijurcatus. Other 

 than these two characteristics, the differences between the species 

 are the shape of the segments and the variation in the position of the 

 armatm-e components. 



Whether the difference in the exopodite makeup of the third leg 

 indicates a fusion of segments (from a 1-3-2 to 1-2-2 condition), a 

 division of segments (from a 1-2-2 to a 1-3-2 condition), or simply 

 a peculiar series in the pertinent armature elements could not be 

 ascertained. The indication is, however, that the distinct difference 

 in the number of segments may possibly be explained by the position 

 and arrangement of the armature. 



The fourth thoracic leg protopodite has a distinct, spikelike projec- 

 tion of the inner distal surface in D. ulua and a distmct, bluntly 

 tipped projection in D. litus. The general armature of the leg and 



Table 11. — Armature of third thoracic legs of four species of Dentigryps. 



