26 



THE APPENDAGES, ANATOMY, AND RELATIONS OF TRILOBITES. 



which, added to the length of the endopodite, 21 mm., makes a distance of 22.5 mm. from 

 the appendifer to the tip of the dactylopodite, showing that if projected straight outward, 

 the endopodi'tes of the thorax would project 5.5 mm. beyond the test, including spines. 



The distance across the axial lobe from appendifer to appendifer on the seventh thoracic 

 segment is 12.5 mm. Measured along the top of the coxopodite, it is 6 mm. from the middle 

 of the notch to the inner end, and measured along the bottom it is 8 mm. From the trun- 

 cated form of the ends it is evident that the coxopodites extended inward and downward 

 from the appendifers, and with the dimensions given above, the inner toothed ends would 

 practically meet on the median line. 



Measurements on the appendages of the pygidia show that on this specimen they extend 

 back about twice as far beyond the edge of the pygidium as they should, all being displaced. 



Specimen No. 65514. 

 Illustrated: Walcott, Smithson. Misc. Coll., vol. 67, 1918, pi. 19, figs. 1-3. 



This specimen is so twisted apart that it is not possible to determine to what segments 

 the appendages belong, but it exhibits the best preserved exopodites I have seen. The 



Fig. 3. Exopodite of Neo- 

 lenus serratus (Rominger), to 

 show form of the lobes of the 

 shaft, and the setae. X 4- 



Fig. 4. Ncolcnus serratus (Rominger). 

 One of the so-called epipodites of specimen 

 65515, showing that it has the same outline 

 as an exopodite (compare figure 3) and 

 fragments of setae on the margin. X 3- 



best one is just in front of the pygidium on the matrix, and shows a form more easily seen 

 than described (our fig. 3). There is a broad, flat, leaf-like shaft, the anterior side of 

 which follows a smooth curve, while in the curve on the posterior side, which is convex 

 backward, there is a re-entrant, setting off a small outer lobe whose length is about one 

 third the length of the whole. This lobe seems to be a continuation of the shaft, and the 

 test of the whole is wrinkled and evidently very thin. The main and distal lobes of the 

 shaft both bear numerous delicate setae, but those of the outer lobe are much shorter and 

 finer than those on the main portion. The latter are flattened and blade-like. 



The anterior edge of the shaft shows a narrow stiffening ridge and the setre are but little 

 longer than its greatest width. The second segment of the pygidium' has another exopodite 

 like this one, but shows faintly the line between the two lobes, as though there were two 



segments. 



This specimen also shows some very well preserved endopodites, but they differ in no way 

 from those described from specimen No. 58589. Walcott mentions two large epipodites pro- 

 jecting from beneath the exopodites. I judge that he has reference to the distal lobes 

 of the exopodites, but as these are continuous with the main shaft, there can be no other 

 interpretation of them than that which I have given above. 



