282 Mr. Newport on the Class Myriapoda, Order Chilopoda, 



dorsal surface, and which, as I have elsewhere* pointed out, acquire in Insects 

 some importance as the paraptera, exist in the Myriapoda only as minute 

 osseous points a little anterior to each spiracle. But those which belong to 

 the ventral arch, and which in Insects are so extensively developed, and are so 

 closely connected with the true ventral plates as to constitute important por- 

 tions of the skeleton, are also well developed in some of the Myriapoda. 

 These are the epimeral plates on each side (figs. 1 and 2, cc). In Scolopendra 

 they consist of one or more ossified plates, which together form a triangular 

 surface at the side of each segment, anterior to the insertion of the coxae {f) 

 of the legs. They are in reality subsidiary to these organs of locomotion, and 

 afford attachment internally to the retractor muscles of the limbs. 



These are the structures which enter into the composition of each segment. 

 They afford a very precise analogy in the Chilopoda with the parts indicated 

 by Audouin as entering into the composition of the segments in true Insects ; 

 in which their actual position in regard to each other varies greatly in dif- 

 ferent species, but their relative position is always the same as in the more 

 rudimentary form of body in the Myriapoda. It is necessary to state, how- 

 ever, that although the structure of the ventral surface in Insects, as described 

 by Audouin, and that of the Myriapoda, as now pointed out by myself, agrees 

 very closely in every particular, yet there is some difference in the identifica- 

 tion of the parts of the dorsal surface. This arises from the circumstance 

 that, in Insects, each segment or division of the thorax is believed to be a 

 compound structure, and was regarded as such by Audouin himself, who con- 

 ceived that each thoracic segment is in reality formed of four segments of one 

 of the lowest types of development of the Articulata. My own investigations 

 are entirely in accordance with this opinion of Audouin, which I am enabled 

 to bear out by an examination of the segments in Myriapoda. In this class 

 of animals the gradual disappearance of some of these suhsegments, as I shall 

 now designate them, is fully apparent, as I shall presently endeavour to show. 

 The names applied by Audouin refer to the whole dorsal plate of each com- 

 pound segment, and not to the three normal pieces of the suhsegments, all 

 which in Insects have completely coalesced into one plate to each distinct 

 segment. Consequently the terms prce-scutum, scutum, scutellum and post- 



* Article Insecta in Cyclopaidia of Practical and Comparative Anatomy, vol. ii. p. 915, 1838, 



