MEGISTHANUS, 33 
of each of which a strong hair arises; the grooves are encircled by an apparently 
elevated broad whitish border, the border showing a microscopical granulation. 
These characters are peculiar to the male sex of the genus Megisthanus, and are 
wanting in the female; the colour of the sternal plate itself is much lighter than that 
of the anal plate, and it is somewhat irregularly distributed—darker on the anterior 
and lateral parts, lighter on the middle; the anal orifice is situated in the middle of 
the anal plate. The side-plates extend beyond the hind coxe, forming a rounded angle 
at their end. ‘The anterior legs are antenniform, long, and without claws; at the top 
of the tarsi there are some densely-set tactile hairs. The second and third pairs of 
legs are strong, somewhat fusiform, bearing on the back of the femora some spine- 
like hairs. ‘The posterior femora have on the back an equidistant row of four spine- 
like hairs and on their lower surface three strong, short, blunt teeth. The remaining 
joints of the legs are irregularly set with hairs. The epistome forms a large triangular 
hood, which is convex above and ends in a short acute angle: during life this piece 
can be moved upwards and laterally; it hides the oral parts but imperfectly, as it is 
surpassed in length by the palpi and, sometimes, by the upper part of the mandibles. 
The palpi are long and simple, sparingly set with hairs, which are more numerous at 
the top of the fourth and fifth joints. The margin of the hypostome bears a blunt 
tooth on each side, and its middle projects into a transparent quadrilobate tongue-like 
piece. The mandibles are strong, their chele rather narrow, bearing numerous irre- 
gular teeth on the inner edge; on the inner surface of the fixed branch of the chela 
a transparent narrow brush projects a little over the top of the mandible ; the movable 
branch seems to be enveloped at the top in a small, transparent, irregularly-folded 
membrane, the border of which is serrulated; on the lateral surface of the movable 
branch there project three transparent appendages, each of which bears some finger- 
like ramifications, and at the base there is a transparent cluster of small spinules. 
2. Body ovate, its anterior margin truncate, slightly convex on the dorsum; dorsal 
plate but moderately shining, rather coarsely punctured, a short semi-erect bristle 
arising from each puncture; colour reddish-brown, the border of the dorsum whitish. 
On each side of the dorsal plate, along its lateral margin, a row of long bristles is 
inserted. The microscopical texture is similar to that of the ventral pieces and hood 
of the male; it consists of a network of fine anastomosing furrows, which leave long, 
narrow, irregular aree between them. Ventral surface convex in the middle, depressed 
and concave at the sides. The whitish interstice between the sternal and lateral 
plates is narrow, that between the sternal and anal plates being broader. ‘The genital 
orifice, which is comparatively large and pentagonal, lies between the 2nd and 3rd 
pairs of coxe. The anterior margin of the anal. plate is straight, its side-margins being 
rounded; the anal orifice is situated in the middle of the plate. The lateral plates 
project into an obtuse angle behind the hind coxe. Epistome and palpi as in the 
male. The hypostome bears no lateral tooth; the tongue-like piece is formed as in 
BIOL. CENTR.-AMER., Arachn. Acar., Vovember 1892. F* 
