190 



THE MYRTAl'ODA OK NORTH AMERICA. 



Fig. 23. 



the base of the antenna). The latter arc generally short, thick, and clumsy, indeed in 

 many genera they seem almost incapable of fulfilling any physiological function. 



The external organs of nutrition are arranged in accordance with two types or plans. 

 The one is adapted for feeding upon decaying vegetable matter, the other for the imbibi- 

 tion of liquid or semi-liquid food. In each there is so much coalescing and atrophying of 

 parts that it is impossible to trace in the adult their homologies. 



lulus marginatus may be taken as an example of the first type. On examining the 

 mouth of this myriapod, it will be found that the anterior or upper boundary is formed 

 by the thin edge of the head; whilst the lower is the edge of a flat plate; (Fig. 23), which 

 forms the lower surface of the buccal cavity and throat. Working between this plate and 

 the head are the jaws. These are very massive, and appear to consist of 

 three joints ; the two proximal of these are firmly connected, almost 

 coalcscent, whilst the distal is united to them by a membranous suture. 

 The basal or proximal part articulates with the head just beneath and 

 posterior to the ocelli, and is so placed as to have its long axis nearly 

 parallel with that of the body. Near to its distal extremity the man- 

 dibles curve abruptly at right angles, so that the distal joints (Fig. 24) present two op- 

 posing surfaces or edges. These are firm, hard, and more or less thin and acute. They are 

 armed with more or less strongly pronounced conical elevations or teeth, 

 and seem well adapted for breaking and cutting off substances. 



The floor of the mouth and under surface of the head is formed by a 

 single thin fiat plate (Tig. 23) composed of several closely united pieces. 

 The outer anterior part is formed on each side by a triangular piece, from 

 which project a pair of short, blunt processes. 



In the sugentia, or second division, the parts about the mouth are all 

 consolidated into a tube-like projection or beak of greater or lesser length. 



Fig. 24. 



Sub Ord. CHILOGNATnA. 



Caput magnum, nonnihil cunciformc. Mandibula maxima. 



Head large, somewhat cuneiform. Mandibles very large. 



The American species of this suborder, which have come under the author's notice, are 

 in this paper arranged in three families, the lulida), Lysiopetalida-, and Polydesmidee. 

 A fourth, the Polyxenidee, is said to be; represented. Of these, the first two constitute 

 the IulMse of Newport, they themselves ranking as subfamilies in the classification of 

 that authority. If any force is to be given to the characters employed by Mr. Gray, his 



