COPEPOD GENUS DENTIGRYPS — LEWIS 373 



dition, D. ulua has a platelike process on either side of the sternal 

 furca while the others either do not have this process or else it is not 

 distinct from the surrounding ventral cephalo thoracic cuticle. 



The adult fu'st thoracic leg is basically similar in all four species, 

 consisting of a 1 -segmented protopodite, a 2-segmented exopodite, 

 and a rudimentary endopodite that gives the leg an indistinctly 

 biramous condition. The differences that occm- do so in what could 

 be called secondary armature elements, elements such as the mem- 

 branes that are present on spines, the individual or small groups of 

 hairlike processes that occur on the segments, the plumose conditions 

 of some of the spines, and small dactyliform or acuminate projections 

 found on some of the spines. These are in contrast to the primary 

 elements such as the spines and setae. The single secondary armature 

 element that appears to be of enough importance to be included in this 

 comparison is a small, acuminate, poorly sclerotized process that pro- 

 jects from the inner surface of each of the inner two terminal spines 

 of the second exopodite segment of D. ulua, D. curtus, and D. litus. 

 Although D. bifurcatus does not possess this process there is, in the 

 same region as the acuminate process on the other species, a distinct 

 membrane, that appears folded and that projects very slightly past 

 the distal end of the terminal spine (the projecting portion is believed 

 to be the folded part of the membrane). As with the first thoracic leg, 

 the comparable difference in the second thoracic leg of all four species 

 occurs in the secondary armatm'e elements. In the second leg how- 

 ever these differences are of such a nature that no distinct trend or 

 grouping can be indicated. 



The third thoracic leg (fig. 13, table 11) has a protopodite-exopodite- 

 endopodite segment number of 1-3-2 in D. ulua and D. bifurcatus 

 and of 1-2-2 in D. curtus and D. litus. The difference in the number 

 of exopodite segments is important in that it suggests a distinct break 

 between D. curtus - D. litus and D. ulua - D. bifurcatus. This break 

 may not be as distinct as it seems, however, as part of the armament 

 of the exopodite of D. curtus is unique and suggests a trarsition 

 between the two groups. The outer margin of the distal two exopodite 

 segments in both groups has four small and naked setae that appear 

 to be divided into two parts. In the 1-3-2 group, the second exopodite 

 segment bears one of these setae on its outer distal lateral sm'face, the 

 remaining three are located on the third segment and are separated 

 from the second segment seta by the division between the segments 

 and by a plumose space. In D. curtus, a member of the 1-2-2 group, 

 all four setae are on the second or distalmost segment but there is a 

 distinct space between the proximalmost of the four and the succeeding 

 three setae. This space is plumose. The separation of the proximal- 

 most from the three succeeding setae and the presence of a plumose 



