T. H. Clark— New Trilobite Appendage. 247 



of it, for the border is thickened and the setae appear to 

 come ont from nnder it. Moreover, adjacent setae, none 

 of which appears to be flexible, emerge from the border 

 at varying angles, a condition which could scarcely obtain 

 were they prolongations of the substance of the exopodite. 

 Inserted setae on trilobite appendages have hitherto been 

 found upon endopodites only. The thickened border 

 extends along the posterior side of the exopodite, which 

 has been crushed fiat, as is shown by the many cracks 

 and slight displacements. 



The endopodite is incomplete. Two or three segments 

 are shown, but it does not appear that the whole member, 

 if completely restored, would be as much as 3 mm. long ; 

 it probably would not exceed 2 mm. It is circular in 

 section, and was undoubtedly stout, for the thickened 

 border of the exopodite may be seen to bulge above it. 



The coxopodite, adjacent to the blunt end of the exopo- 

 dite, is small, but probably incomplete. It is roughly 

 rectangular, and crushed flat. 



Below this are two fragments which the writer inter- 

 prets as a second coxopodite, and the base of a second 

 exopodite, both belonging to a single segment. Above 

 the whole is a large patch of black, but less shiny, mate- 

 rial, shown by shading in the sketch, which, if it be part 

 of this assemblage at all, might represent a fragment of 

 the ventral membrane of the trilobite. This is purely 

 conjectural, but it lies where the ventral membrane would 

 be looked for, immediately above the exopodite. 



Apart from the presence of inserted setae in the exopo- 

 dite, the most remarkable feature about this specimen is 

 the relation in size between the exopodite and the endopo- 

 dite. That the animal which bore this appendage was 

 not adapted for crawling is certain ; no trilobite with such 

 reduced endopodites could have been a successful ben- 

 thonic inhabitant. On the other hand, the large paddle- 

 like exopodite might well have been adapted to a nectonic 

 or a planktonic mode of existence. This is in accord with 

 the conclusion reached with regard to the whole Levis 

 fauna. 



This limb does not agree exactly with any of the known 

 trilobite appendages. In Neolenus the endopodites are 

 relatively very large, much longer than the exopodites. 



