262 Records of the Indian Museum. [Vol. XIII, 



Rhynchoplax exiguus appears to be related to R. inachoides 

 (Alcock), but is distinguished by the broader carapace, shorter 

 rostral lobes, much shorter walking legs and larger dactylar teeth. 



The specimens were obtained by Dr. Annandale in the Tale 

 Sap in Peninsular Siam. They were found on the mainland oppo- 

 site the western end of Koh Yaw, living in lumps of turf that had 

 fallen into the lake owing to the undermining of the bank. The 

 water in the vicinity was brackish, the specific gravity being about 

 1*00625 (corrected). 



The types bear the number 9743/10 Zool. Surv. Ind. 



Rhynchoplax introvcrsus, sp. nov. 



The carapace is ovate and is widest behind its middle point; 

 its greatest breadth slightly exceeds its length, rostrum included. 

 The upper surface is much sunken ; in addition to the usual 

 grooves, which are sharply demarcated, the branchial regions are 

 traversed by a fine oblique line. There is an obscure anguktion 

 on the anterolateral margin midway between the eye and the 

 chelipedes, but there are no teeth in this position and no tooth or 

 process above the base of the first walking legs. At first sight the 

 antero-lateral and postero-lateral borders on each side appear to 

 be discontinuous (tex-fig. iia). This, however, is due to the fact 

 that the lateral walls of the branchial chamber project on either 

 side and are reflected upwards, so as to form a crest which is 

 actually higher than the true postero lateral border. This border 

 is continued as a low ridge within and parallel to the branchial 

 crest. The posterior margin is short, with a slight emargination 

 on either side opposite the last leg. The rostrum is composed of 

 three blunt processes, the median horizontal, parallel-sided and 

 about twice as long as broad, the two others shorter, and project- 

 ing obliquely upwards. 



Almost the whole of the eye is visible from above, together 

 with a small post-ocular tooth. The antennules fold beneath the 

 front and are separated at the base by a blunt longitudinal ridge. 

 The epistome is long. The external maxillipedes are of the usual 

 form; they gape widely in the middle line and the merus is a little 

 longer than the ischium. The exognath is almost entirely exposed 

 (text-fig. lib). 



The chelipedes are stout and clothed with fine hairs. The 

 merus is without teeth. The chela is stout in the male, about two 

 and a half times as long as broad, with the palm slightly swollen. 

 The fingers are fully one and a half times as long as the upper 

 border of the palm ; they meet throughout their length when the 

 claw is closed and their inner margins bear five or six interlocking 

 teeth. 



The walking legs are slender ; the second pair is about two 

 and a third times as long as the carapace and rostrum. The merus 

 in all four pairs bears a small tooth at the distal end of the 

 upper border. The dactylus is moderately curved and is armed 



