THE JOINTED ANIMALS 



SUMATRAN PILL MILLIPEDE, Sphceopceus. 

 (Natural size.) 



of trees. A species of the typical Polyxenus is shown in the illustration. In 

 the Chilognatha the antennae are seven jointed, and the body is not furnished 

 with tufts of scale-like hairs. The group is divisible into the orders Oniscomorpha, 

 lyimacomorpha, and Helminthomorpha. In the former, as represented by the pill 



millipedes, the body is short and broad, con- 

 vex above and flat below, with the second and 

 last segments enormously enlarged, and 

 capable of being rolled up into a ball. The 

 skeletal pieces which compose the segments 

 are distinct and movably jointed together. 

 Each typical segment consists of seven 

 pieces; a large and vaulted tergum forming 

 the upper surface and concealing the legs; 



while beneath this on each side there is a small pleural piece, and between this and 

 the two legs two still smaller tracheal plates bearing the stigmata. The legs 

 are in contact in the middle line of the body, and those of the last pair are enlarged 

 in the male and transformed into a pair of clasping organs. Of the two families 

 into which the order is divided the Glomeridce, or small pill millipedes of Europe, 

 have the antennae close together upon the front of the head, the eyes with a single 

 row, of ocelli, and the body consists of only 

 twelve segments. In the Zephroniidce , or 

 large tropical pill millipedes, the antennas 

 are situated on the sides of the head, the 

 eyes are composed of a spherical cluster of 

 ocelli, andthe body consists of thirteen seg- 

 ments. In the South-African genus 

 Sphcerotherium the last pair of legs in the 

 male is furnished with a well developed 

 stridulating apparatus, consisting of a finely 

 ridged plate, which by being rubbed against 

 a set of granules on the inner surface of the 

 last tergal shield, gives rise to an audible 

 sound. Although no representatives occur 

 in America, the order is spread over the 



Eastern Hemisphere, the Glomeridce ranging over Europe and thence into India and 

 Borneo, while the Zephroniidce occur in South Africa, Madagascar, India, the Malay 

 Peninsula, Australia, and New Zealand. 



The Umacomorpha, or slug-like millipedes, form a small group, containing but 

 two known genera and three species included in the family Glomeridesmidce. The 

 body is composed of nineteen or twenty segments, all of them being approximately 

 equal in size and similar in form, and none of them abruptly larger than the rest. 

 The body is capable of being spirally coiled; its segments are formed much as in the 

 Oniscomorpha, but the tracheal plates are not distinct. The last tergal plate, al- 

 though small, forms a hood which covers over the last pair of legs, and these are 

 modified in form as in the males of the Oniscomorpha. The rest of the legs are 



-If 



ENGLISH PILL MILLIPEDE. 

 (Natural size.) 



