ON THE CHILOPODA OF NORTH AMERICA. 





tor muscles of the legs. 



ner formed from four pieces — the primitive sternum (fig. 1, a) and episternum, (fig. 1, h.) 



Fig. 1. Close to the spiracles, and belonging 



to the dorsal section, are two osseous 

 points, the rudiments of the parap- 

 tera, which attain to some import- 

 ance among the Hexapoda. At the 

 insertion of the legs are several small 

 plates, the epimera (fig. 1, c.) They 

 afford points of origin to the retrac- 

 The posterior of the two subsegments forms the mass of the 

 segment ; but the scutum of the anterior is represented by a raised band on the front 

 of the main scutum. The ventral portions of it are, however, much more distinct. 

 We will find a series of small plates anterior to the sternum representing two primi- 

 tive sterna (fig. 1, s) and episterna (fig. 1, e) as well as epimeral plates. 



The legs contain each a coxa (fig. 1, cl) a femur, b, a tibia, t, a tarsus, g, and meta- 

 tarsal joints, m, n. The coxae are generally small, except those of the posterior pair of 

 legs, which are often of immense size and are known as the lateral anal appendages. 

 Among the Cermatiidaa and Lithobiidse, however, they 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 Cermatiidse 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 Cermatiidse, in which it is the most 

 prominent part of the body, supporting a pair of very large compound eyes and almost 

 completely concealing the strikingly atrophied basilar segment. Traces of the division 

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

 especially among the Lithobiidse, but the embryological labors of Mr. Newport have 

 shown conclusively that it is so formed ; to whose invaluable papers, in the XIX. 

 volume of the Linnasan Transactions, we would here acknowledge our indebtedness. 

 The head in the Scolopendridse 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 Cermatiidaa. 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 subsegment is en- 

 tirely separated from the rest, its scutum existing as a small plate immediately poste- 

 rior to the cephalic, and is here called the prebasilar. In the other genera of the Geo- 

 philidae 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 the head, comprising as it does the organs of 



