NEOLENUS. 



2 9 



For convenience of discussion, these lobes may be called Nos. i, 2, 3, and 4, the last 

 being the posterior one (fig. 5). This lobe is best shown on the matrix, where the anterior 

 end is seen to be margined by stout spines, while the posterior end lies over the endopodite 

 and under the exopodite behind it. No. 3 is sunk below the level of the others, and only 

 a part of it has been uncovered. Its margin bears strong spines of different sizes. Its 

 full shape can not be made out, but it has neither the shape nor the form of spines shown 

 in figure 3, plate 20 (1918). Lobes 2 and i and another lobe in front of i seem to form 

 a continuous series and to be part of a single appendage. They are all in one plane, arc 

 so continuous that the joints between them can be made out with difficulty and if they do 

 belong together, can easily be explained. 



Fig. 5. A sketch 

 of the so-called 

 exites of Neolenus 

 serratus (Rom- 

 inger), to show the 

 form and the char- 

 acter of the spines. 

 X2. 



Fig. 6. Endop- 

 odite of a cephalic 

 appendage of Neo- 

 lenus serratus 

 (Rominger), show- 

 ing the very broad 

 coxopodite. X 2. 



Before calling these structures new organs not previously seen on trilobites, it is of 

 course necessary to inquire if they can be interpreted as representing any known structures. 

 That they can not be exopodites is obvious, since they are bordered by short stout spines 

 instead of setas. The same stout spines that negate the above possible explanation at once 

 suggest that they are coxopodites (compare fig 6). At first sight, the so-called exites seem 

 too wide and too rounded to be so interpreted, but if reference be had to the specimens 

 rather than the figures, it will be noted that the only well preserved structure (No. 2) is 

 longer than wide, has spines only on one side and one end, and does not differ greatly 

 from the coxopodite of specimen No. 58589 (pi. 18, 1918). If structures 2, i, and the 

 segment ahead of i are really parts of one appendage, it can only be an endopodite, of 

 which No. 2 is the coxopodite, No. I the basipodite, and the next segment the ischiopo- 

 dite. If one looks carefully, there are no traces of spines on either end of No. i, but only 

 on the margin. The extreme width of No. 2 is against this interpretation as a coxopo- 

 dite (see, however, fig. 6), but it may be rolled out very flat, as this is an unusually 



