142 THE MYRIAPODA OF NORTH AMERICA. 



a series of small plates anterior to the sternum, representing the two parts of the primitive 

 sternum (Fig. 2, s), and the two episterna (Fig. 2, e), as well as the epimeral plates. 



The legs contain each a coxa (Fig. 2, d), a femur, b, a tibia, t, a tarsus, g, and meta- 

 tarsal joints, in, n. The coxa? are generally small, except those of the posterior pair of 

 legs, which are often very large, and are known as the lateral anal appendages. Among 

 the Cermatiidae and Lithobiida?, however, they all attain to a considerable size. The 

 metatarsal joints vary very much ; in the genus Scolopendra there are but two to each 

 leg, whilst among the Cermatiidae there are a great number. 



The head in the Chilopoda is composed of eight subsegments consolidated into two or 

 more segments, as was first shown by Mr. Newport. The first segment is styled the 

 cephalic. It reaches its maximum size in the Cermatiida?, in which it is the most promi- 

 nent part of the body, supporting a pair of very large compound eyes, and almost com- 

 pletely concealing the strikingly atrophied basilar segment. Traces of the division into 

 the four subsegments, that existed during embryonic life, are occasionally met with, espe- 

 cially among the Lithobiida?, but the embryological labors of Mr. Newport have shown 

 conclusively that it is so formed. The head in the Scolopendrida? has, in addition to the 

 cephalic segment, another one of variable size ; this is the basilar. It is also found well 

 developed in all the other families except the Cermatiida?. Near its anterior border there 

 is often found a deep crescentic groove ; the portion separated by this from the main 

 body, is called the prebasilar fold or subsegment. In the genus Mecistocephalus this sub- 

 segment is entirely separated from the rest, its scutum existing as a small plate imme- 

 diately posterior to the cephalic, and is there called the prebasilar. In the other genera of 

 the Geophilidae this is wanting, but there exists posteriorly another segment, answering to 

 the posterior portion of the basilar of the Scolopendrida?. It is the subbasilar of Newport. 

 The under surface of tin- head, comprising as it does the organs of nutrition, is much 

 more complicated than the upper, and, in order to show the relations of parts more clearly, 

 I will trace them out minutely in the genus Scolopendra, where perhaps their analogy 

 is most easily discovered. 



On examining the under side of the head of a specimen of the genus Scolopendra, we 

 will find a band constituting the most anterior portion, with which the antennae partially 

 articulate; this band I take to be the anchylosed primitive sterna and episterna of the 

 first cephalic subsegment, of which the antennae arc the appendages. Just posterior and 

 inferior to the eyes, we will see what is apparently an inversion of the cephalic scutum, 

 hut closer examination shows it. to consisl of two small plates, the superior exterior 

 (Fig. :!, e), uniting with the scutum by suture, the inferior interior (Fig. :5, h) approxi- 

 mating to the other plate; the first of these is the atrophied episternum, the other the 

 primitive sternum of the second cephalic subsegment. United with this sternum by 



