ARTHROPODA. ID 



one of which in Chilopoda is abortive, are equally developed in 

 Chilognatha, and each carries a distinct appendage. The terga, 

 however, are confluent, so that the double nature of each body- 

 segment is only evident when the ventral surface is examined, 

 where two pairs of appendages will be found attached to each 

 segment. The segmental appendages are composed of six 

 joints, coxa, tibia, femur, metatarsus, tarsus, and claw. The an- 

 terior appendages are the smallest, but they gradually increase 

 in size posteriorly; and the hindermost pairs are directed back- 

 wards and not outwards, as is the case with the anterior ones. 

 The last pair is very much larger than any of the rest, curves 

 inwards, and by mutual apposition forms an efficient clasping 

 apparatus. The anus opens on the under surface of the last 

 segment. In several of the segments a pair of small, crescentic, 

 laterally placed slits surrounded by prominent chitinous lips 

 is to be seen a little inferior to the dorsal arc : these are the 

 ' stigmata.' 



The head is probably formed by the fusion of at least five 

 of the most anterior segments. The superior surface is formed 

 by a broad, shield-like plate, quite smooth, and devoid of 

 sutures, with the exception of a faint median groove. To the 

 anterior margin of this plate is attached a pair of multiarti- 

 culate antennae consisting of not fewer than seven segments. 

 In this respect the Order Chilopoda, to which this species 

 belongs, differs from the Order Chilognatha, in whicb the 

 antennas are composed of fewer than seven segments. At the 

 base of the antenna?, and external to them, are four sessile 

 'oculi.' On the inferior surface of the head, in addition to the 

 antennas already described, the following appendages are to be 

 seen. First, a pair of mandibles, toothed on their inner edges, 

 and carrying small rudimentary palpi on their outer edge. 

 Secondly, two pairs of maxillss, of which the anterior pair is 

 jointed, palpiform, and forms the external elements of the 

 labium, while the posterior pair is composed of two small 

 conical pieces applied together in the mesial line, but not 

 united, and constituting the mesial part of the 'labium.' 



The appendages hitherto enumerated belong to the head, 

 the remainder, proceeding backwards, to regions which in the 

 Lobster are termed thoracic, abdominal and post-abdominal. 



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