THW AITESIA. 197 
Thwaitesia margaritifera, Cambr., but the male above described may be readily distin- 
guished by the different relative proportion of the radial and cubital joints of the palpi. 
In the Ceylon spider the cubital is a little longer than the radial, whereas in 7. affinis 
the latter is nearly double the length of the former. The palpal organs are very similar 
in the two species. 
Thwaitesia vittata. 
Achea vittata, Cambr. antea, p. 130, t. 17. fig. 11. 
By an inadvertence this spider was (J. c. supra) described as an Achea, from which 
genus it is widely removed. 
In his work ‘Die Spinnen Amerikas: Theridiide,’ 1884, the late Count Keyserling 
appears to have quite misapprehended the typical characters of the genus Achwa 
(Cambr.) and to have described there (under Achwa) several species nearly allied to 
Thwaitesia vittata. ‘This last I believe to belong to the genus Thwaitesia as originally 
characterized. According to M. Simon (‘ Hist. Nat. des Araignées’), 7. vittata and 
others (included, as above mentioned, by Keyserling under Achwa) should be retained 
under Theridion, while Thwaitesia is kept for the type Z. margaritifera, Cambr., and 
one or two others scarcely specifically different from it. The whole group, Theridion, 
Walck., has presented immense difficulties which cannot be satisfactorily surmounted 
without the careful study of far more materials from tropical regions than we have yet 
received, while at the same time—paradoxical as it sounds—it is the abundance 
of recent additions to our collections from the tropics which has mainly created 
the difficulties. Theridion, as restricted now by M. Simon, seems to me an utterly 
unworkable group. 
Thwaitesia lepida, sp. n. 
Adult female, length—to summit of abdomen 33 lines, from spinners to falces 3 lines, from summit to spinners 
nearly 23 lines. 
Cephalothorax rather longer than broad ; lateral marginal impressions at caput slight, upper convexity small. 
Caput no higher than the thorax; thoracic indentation large and deep ; indentations at junction of caput 
and thorax strong; ocular area a little prominent; clypeus strongly impressed transversely below the 
eyes, prominent at the lower margin, which is well rounded, its height considerably exceeding half that 
of the facial space; colour dull yellow-brown, hinder part of caput a little paler; junction of caput and 
thorax marked with a blackish spot. 
Eyes normal, subequal, scarcely differing in size ; posterior row, looked at from above and a little behind straight, 
the two centrals considerably nearer together than to the hind-laterals; central quadrangle forming 
almost a square, slightly broader than long; curve of anterior row not very strong, its convexity directed 
forwards; interval between the fore-centrals much greater than that between them and the fore-laterals. 
Legs long, moderately strong, unequal, 1, 4, 2, 3, those of the first pair about three and a half times the 
longest length of the spider. Colour pale yellow, distinctly annulated, chiefly at the extremities of the 
joints, with dark red-brown, approaching in some parts to black; the femora of the first and second 
pairs are also marked with small dark brown linear spots, some forming almost a continuous line. They 
are furnished with hairs only. 
Falces moderate in length and strength, straight, similar in colour to the cephalothorax. 
Maville strong, straight, a little inclined towards the labium, of a dark brown colour. 
Labiwm more than double as broad as it is high, somewhat semicircular. 
