XO. 3 BURGESS SHALE FOSSILS WALCOTT 3 1 



Cephalic appendages. — These consist of antennae, mandibles, simple 

 slender maxillulae. and slender maxillae. The proximal joints of the 

 cephalic appendages are so badly crushed and matted together beneath 

 the labrum or just back of it that it has been very difficult to determine 

 exactly their form and relations to each other, but it is highly probable 

 that they were arranged as in the restoration (text fig. 9). 



Antennae. — The antennae are long, slender, and many-jointed, with 

 fine spines at the distal end of each joint. As far as may be determined, 

 the proximal joint was attached to the ventral surface beneath the 

 postero-lateral angle of the labrum just in advance of the mandible. 

 There is no evidence that it served as a jaw or manducatory organ 

 except that in specimens preserving them their inner (proximal) end 

 is in front of and adjoining the large proximal joint of the mandibles 

 (see figs. 3, 6, and 7, pi. 22). 



Mandibles. — The mandibles are formed of a strong proximal joint 

 with four short, strong joints followed by five slender, elongate joints 

 (see fig. 9), the latter being almost covered with very fine setae that 

 give a plumose appearance to the appendage as it extends out beyond 

 the great backward curving spines of the carapace. I examined hun- 

 dreds of specimens before finding a proximal joint with its inner end 

 sufficiently well preserved to suggest the character of its masticatory 

 surface ; two specimens indicate that it is as shown in figure 7, 

 plate 22, and in the restoration. There is no evidence as to whether 

 the proximal joint is composed of one long joint or two closely united 

 short joints. The usual location of the mandibles in well preserved 

 specimens is shown by figures i and 2, plate 22. 



Maxilhdae. — These are long, slender, and with about 10 slender 

 joints. They look like thoracic legs (endopodite) but their position 

 and slender joints serve to distinguish them. Portions of them may be 

 seen in figures i and 2, plate 22. 



Maxillae. — As far as known the maxillae are formed of joints a 

 little longer than those of the maxillula and about the same diameter ; 

 both appear to have been slender, rather closely jointed, simple ap- 

 pendages as far as the endopodite was concerned ; there is strong 

 evidence that an exopodite was present, similar to those of the exop- 

 odites of the trunk appendages, but they have not been seen directly 

 attached to the protopodite ; where the parting of the shale is on the 

 plane of the exopodites they are usually present next to the mandible 

 and directly over the position of the maxillulae and maxillae, which 

 suggests strongly that they were present. 



The maxillulae and maxillae were so slender that they are usually 

 absent as the result of having been torn ofif or crushed between the 

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