A .11 T I C L E VI I. 



THE MYEIAPODA OF NORTH AMERICA.* 



Head June 16, 1865.1 



The Myriapoda are air-breathing apterous articulata characterized by the distinctness 

 of the head from the body ; the strongly marked segmentation of the latter, and its 

 method of development. 



The head varies very much in size and the perfection of its organization, but is always 

 separate and distinct. The organs of special sense are very well developed in all but the 

 lowest orders. The eyes are in one family compound, in the others stemmatous and single 

 or numerous, or else entirely wanting. 



The body is composed of a varying number of segments, most of which are merely a 

 repetition of the preceding. The number varies from sixteen to several hundred. As a 

 general rule, the fewer the segments the higher the organization. Each perfected seg- 

 ment is formed from two subsegments, cither by their coalescence and mutual growth, or 



* Most of the material on which this paper is founded has boon furnished by the Smithsonian Institute, Mu- 

 seum of Comparative Anatomy and Zoology of Cambridge, and the Academy of Natural Sciences of Philadelphia. 

 By far the larger portion was received from the Smithsonian, much of which was collected by Mr. Kennicott in 

 South Illinois, and E. J. Walker in Western Pennsylvania. The latter gentleman sent some seven or eight thou- 

 sand specimens. Prof. Manly Miles, of the State Agricultural College of Michigan, also furnished several now 

 species from that State. I have also examined a small collection of Canadian Myriapoda, received from Prof. 

 Dawson, of Montreal. 



In " North America," Mexico is not intended to be included, since although perhaps geographically it is a part of 

 the latter, yet its Fauna is much more closely allied to that of Central than North America. The monograph was 

 originally commenced at the suggestion of Prof. Baird, some four years ago, to form part of the Miscellaneous Col- 

 lections of the Smithsonian Institute, and the wood-cuts have boon executed at the expense of the Institution. As 

 the publication of this series has been temporarily suspended, with the consent of Prof. Henry the paper was 

 offered to the Philosophical Society. The wood-cuts were drawn by Mr. Edward J. Nolan, under my personal 

 supervision, and every effort has been made to have them entirely accurate. 



f The original MS. of this memoir was presented to the Smithsonian Institute, and destroyed in the confla- 

 gration of part of the Smithsonian building in the winter of 1864-5. It was then rewritten and presented for pub- 

 lication to the A. P. S. by the author, with the permission of the Secretary of the S. I., who granted likewise the 

 use of such wood-cuts as were already either drawn or executed, about 60 in all. [Sec. A. P. S.] 

 vol. xn i — 18 



