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 proportionate 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 antennæ 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, reproduced, 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, Illiger.
Caput magnum. Oculi prominentes. Stomata dorsalia latera incrassata.
Head large. Eyes prominent. Dorsal stomata with their sides thickened.
Scutigera, Lamarck, Anim. Sans. Vertb.
Selista, Rafinesque, 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: scutis spinulis numerosis asperatis, valde imbricatis, angulis rotundatis, marginibus elevatis sed tenuibus et "spinis quam in Cerm. coleoptrata evidentioribus;" lateribus plerumque rufescenti tinctis; femoribus singulo annulo unico saturate viridi; tibiis et tarsis biannulatis; pedum pari postremo in mare corpore vix ¼ longiore (in femina bis longiore); articulo metatarsali primo secundo fere quater longiore, sequentibus quinque conjunctis fere æquali) superficie ventrali flavescente; sternis mediis canaliculatis.
vol. xiii.—19
