176 



THE MTRIAI'ODA OF NORTH AMERICA. 



The family character of this group which first attracts attention, is the large number 

 of segments, each of which is composed of two unequal subsegments. The boundaries of 

 the respective scuta of each pair of the latter are well marked by sutures, &c, but the 

 sterna are completely consolidated. The head varies in form, size, &c, and furnishes the 

 principal generic characters. The number of joints of the antenna? is fixed for the family, 

 but nevertheless good specific, and even generic, characters, are derivable from these 

 organs. The most important specific characters besides those before alluded to are founded 

 upon, firstly, the peculiarities as to size, shape, proportion, &c, of the component portions 

 of the head and its appendages ; secondly, the color and form of the body, and the number 

 of segments composing it ; thirdly, the structure of the legs, especially of the last pair ; and, 

 finally, the markings and sutures of the scuta and sterna. I have never had an opportu- 

 nity of examining very large suites of specimens, so as to determine positively the con- 

 stancy of the various characters enumerated, but they probably do not vary a great deal. 



Gen. 1. MECISTOCEPHALUS, Nevrp* 



Seo-raentum cephalicum elongatum, angustum, latitudine plus duplo longius. Antenna? approximate, articulis 

 obconicis. Subsegmentum prebasale sejunctutn sed basale subbasaleque ooalita. Mandibular magna?, intus den- 

 ticulate. (Fig. 18.) 



Cepbalic segment elongate, narrow, more than twice as long as broad. Antenna? approximate; articles obconic. 

 Prebasal subsegment separate, but the basal and subbasal coalescent. Mandibles large, within denticulate. 



M. FULVBS. 



M. fulvus, politus; capite dilute aurantiaco, punctata, pilis Iongis rigidis paucis; segmento cephalico antice 

 truncate, postice illico angustato et vis truncate; antennis Iongis, pilis Iongis rigidis multis; labio 

 profundi 1 punctate, antice emarginato, medio sulco impresso; mandibulis distincte punctatis, pilis 

 rigidis paucis, quadridentatis ; segmento anali piloso ; pedibus pilis Iongis, paribus .>7. 



Fulvous, polished; head light orange, punctate, with a few long rigid hails; cephalic segment 



anteriorly truncate ; posteriorly rapidly narrowed and scarcely truncate; antennae with many long 



rigid hairs; labium profoundly punctate, anteriorly emarginate, impressed with a median sulcus; 



| mandibles distinctly punctate, with a few rigid hairs, quadridentate ; anal segment pilose; feet with 



long hairs, 57 pairs. 



M. pi t.\ i s, Wood, Journ. A. N. S., new series, 1863, vol. v. p. 11. 

 Geophili s attenuati -. Suy, Jouro. A. N. S, 1st series, vol. ii. 



The cephalic segment is scarcelj narrowed at all, except at the posterior end, where it 

 is rapidly contracted, being indeed rounded off. The body is slender and polished. The 



* 1'iue. Zool. Society, December, IS 12, p. 179. 



