Page:Wood 1865 - The Myriapoda of North America.djvu/41

176 The family character of this group which first attracts attention, is the large number of segments, each of which is composed of two unequal subsegments. The boundaries of the respective scuta of each pair of the latter are well marked by sutures, &c., but the sterna are completely consolidated. The head varies in form, size, &c., and furnishes the principal generic characters. The number of joints of the antennæ is fixed for the family, but nevertheless good specific, and even generic, characters, are derivable from these organs. The most important specific characters besides those before alluded to are founded upon, firstly, the peculiarities as to size, shape, proportion, &c., of the component portions of the head and its appendages; secondly, the color and form of the body, and the number of segments composing it; thirdly, the structure of the legs, especially of the last pair; and, finally, the markings and sutures of the scuta and sterna. I have never had an opportunity of examining very large suites of specimens, so as to determine positively the constancy of the various characters enumerated, but they probably do not vary a great deal.

The cephalic segment is scarcely narrowed at all, except at the posterior end, where it is rapidly contracted, being indeed rounded off. The body is slender and polished. The