TUE MYKIAPODA OF NORTH AMERICA. 145 



spines, encircling the joints. The sides have nine pairs of spiracles, the openings into the 

 tracheal vessels. The anal segment in the female is elongate, and the external organs of 

 generation are furnished with a pair of forceps, replaced in the male by a pair of styliform 

 appendages. The sterna are small ; the last, the sixteenth, is merely rudimentary. It is 

 very evident that the number of segments is sixteen, and that each scutum is formed by 

 the coalition of two neighboring ones. The pattern of coloration is peculiar to this family ; 

 it consists of longitudinal stripes on the body and annuli on the appendages. There has 

 as yet only one genus been found in this family, among which so great a uniformity 

 exists as to make the distinguishing of species a task of considerable difficulty. 



The color is probably a good specific character, but is seldom, if ever, preserved. I 

 have seen specimens of S. forceps changed almost immediately to green or blue, or, more 

 commonly, bright purple, by alcohol. 



Any anatomical characters are very obscure ; but Mr. Newport considers the propor- 

 tionate lengths of the metatarsal joints as constant, and I have found them so, as far as 

 my limited observations have gone. 



The lengths of the antenna? and posterior pair of legs, as compared with the body, are 

 also probably good characters, but very liable to misinterpretation ; for it is difficult, often 

 impossible, to tell when the former are broken and when the latter are imperfect, repro- 

 duced, appendages. Mr. Templeton, who first suggested these points, also makes use of 

 the size of the marginal spines of the scuta in his descriptions. The peculiarities of the 

 surface of the scuta also appear to be good secondary characters. 



Gen. 1. CERMATIA, llliger. 



Caput magnum. Oculi prominentes. Stomata dorsalia latera incrassata. 

 Head large. Eyes prominent. Dorsal stomata with their sides thickened. 



Scutigeea, Lamarck, Anim. Sans. Vertb. 

 Selista, Rajinesque, Annals of Nature. 



C. FORCEPS. 



C. viridi-brunnea, fasciis tribus longitudinalibus nigro-viridibus ; capite antice breviter piloso, et linea 

 depressa longitudinale mediana et ante oculos utrinque altera curvata, et altera tranversa inter oculos, et 

 postice depressione lata insculpto ; antennis mandibulisque ferrugineis : seutis spinulis numerosis asperatis, 

 valdc imbricatis, angulis rotundatis, marginibus elevatis sed tenuibus et "spinis quain in Cerm. coleoptrata 

 evidentioribus;" lateribus plerumque rufeseenti tinctis ; femoribus singulo annulo unico saturate viridi j tibiis 

 et tarsis biannulatis ; pedum pari postremo in mare corpore vix 4 longiore (in femina bis longiore) ; articulo 

 metatarsal primo seeundo fere quater longiore, sequentibus quinque conjunetis fere sequali ; superficie ventrali 

 flavescente ; sternis mediis canaliculars. 



VOL. XIII. — 19 



