1897] FOSSIL APODIDAE 399 
limbs (see fig. 6), each pair being provided with a pair of abdominal 
ganglia. It was, of course, more or less of an assumption that these 
limbs and ganglia represented true segments, because to all appear- 
ance the true segments are marked off on the body as shown in the 
fig. 6. Further, authors were not wanting who definitely claimed 
that the apparent segmentation was the true one, and that the 
multiplication of the limbs, as many as four, five, and even six to 
one single segment, was due to some kind of secondary reduplication 
1. Protocaris marshi, Walcott ; 2. Dipeltis carri, Schuchert ; 3. Dipeltis diplodiscus, 
Packard ; 4-5. Another specimen of the same, showing the under surface and part 
of the upper with the eyes; 6. Apus glacialis, var. spitzbergensis from the side, 
with left half of the carapace cut away to show the whole trunk ; bp. left limbs of 
the eleventh segment modified into a brood-pouch, p. pore leading into the water 
sacs over the eyes. [Figs. 1-5 after Schuchert. | 
of organs on one and the same segment. The present writer, on the 
contrary, maintained that, as at the front end of the body each pair 
of limbs with its pair of ganglia corresponded with a true body seg- 
ment, the whole series of the limbs should be taken as true seg- 
mental structures, and where, after the eleventh segment, marked 
by its brood pouch (bp.), the limbs begin to diminish in size, there 
being more than one to each external division of the body, these 
