800 The American Naturalist. [September, 
Fic. 7. Young of Mebalia geoffroyi. (After Metschnikoff.) 
single example of Protocaris known, has probably been sub- 
jected to some horizontal distortion in the shale, giving the 
carapace a disproportionate size with reference to Apus, possi- 
bly also serving to obliterate any external evidence of ocular 
nodes which may have existed, but the remarkable closeness 
in the form of the abdominal segments, the degree of segmen- 
tation and the single strong pair of caudal processes, renders 
it highly probable that in Protocaris, we have to do with an 
apudiform phyllopod rather than with a nebalioid phyllocarid. 
G. 8. Protocaris marshii. Fic. 9. Apus equalis. (After 
"eid Walcott.) ` Packard.) 
. Among the bivalved genera, not including Estheria and 
Leaia which Messrs, Jones and Woodward have placed with 
the Phyllocarids, there is throughout a general resemblance to 
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