ON THE CHILOPODA OF NORTH AMERICA. 



nutrition, is much more complicated than the upper, and, in order to show the rela- 

 tions of parts more clearly, we will first trace them out minutely in the genus Scolo- 

 penclra, 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 antennas 

 partially articulate ; this band we take to be the anchylosed primitive sterna and 

 episterna of the first cephalic subsegment, of which the antenna? are the appendages. 

 Just posterior and inferior to the eyes, we will see what is apparently an inversion of 

 the cephalic scutum, but closer examination shows it to consist of two small plates, 

 the superior exterior, (fig. 2, e,) uniting with the scutum by suture, the inferior 



Fis 



interior (fig. 2, h) approximating 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 suture we will find posteriorly 

 a larger plate (fig. 2, d) which articulate on its inner side 

 with another obliquely transverse plate, (&,) which also 

 is conjoined on its inner side by another, (c,) and that 

 too by another, and finally in the centre there is a small 

 tooth, as it were. These plates are respectively the 

 coxa, femur, tibia, tarsus, and the rudimentary metatar- 

 sse (the central tooth) of the atrophied and misplaced ap- 

 pendages of the second cephalic subsegment. The tibia 

 and tarsus are generally anchylosed together, but we 

 have seen them separate. Conjoined and posterior to the coxa of the second cephalic 

 subsegment we will find a large plate (a) articulating with the cephalic scutum by 

 suture ; this we take to be the primitive sternum and episternum of thethird cephalic 

 subsegment atrophied and fused together ; to it the true maxilla? are articulated. 

 These consist each of, first an elongated crooked plate (the coxa) articulating with two 

 plates, the exterior of which (the femur) is armed with a tubercle, as in the mandibles, 

 posterior legs, &c. ; the inner plate is the tibia ; these two plates articulate at their 

 distal end with a third, the tarsus and metatarsus coalescent, but with the line of 

 their junction very apparent. The inaxillaa we believe to be the appendages of 

 the third cephalic subsegment. Just anterior to the primitive sternum of the first, and 

 posterior to that of the third, are often found some small plates which wo believe 

 to be epimeral. But the largest of the latter is probably the episternum Fi s- 3 - 



of the fourth cephalic subsetiment, which is scarcely to be found else- /i r\ 



where. Proceeding still posteriorly we come to the maxillary palpi. X 



(fig. 3,) which are possessed each of a distinct femur, (/,) tibia, (x,) \y ^J) 



and tavso-metatarsal joint, (»*.) They are the appendages of the fourth cephalic sub- 



