918 DR. W. T. CALMAN ON 



specimen (81.9), is a trille less than half the distance between the 

 former crest and the frontal margin, is about 2/5ths of that 

 distance in the largest specimen from 85.18, l/3rd in the largest 

 fi^om 82.6, and only about l/4th in an adult female from 80.27, 

 while in the smallest specimen from 85.18 the two crests are all 

 but continuous ; (2) the roughness of the sni'face of the carapace, 

 which, in most of the specimens, is in accordance with the 

 published descriptions and figures, becomes notably reduced in 

 the specimens from Betsileo registered under the numbers 82.6 

 and 80.27 ; in these, the whole carapace is much smoother, with 

 only a few oblique granules or raised lines near the antero-lateral 

 margins and on the posterior branchial regions, and one or two 

 obsolescent granules on the front ; it is to be noted that the 

 granulation or serration of the antero-lateral margins themselves 

 is not correlated with the general roughness or smoothness of the 

 surface, being stronger in the Betsileo specimens than in the much 

 rougher specimens from 85.18. 



In the smaller specimens of this series, especially in the two 

 smallest from 85.18, the external orbital notch becomes very 

 shallow or is altogether obliterated, and the outline of the carapace 

 is more quadrilateral than in larger specimens. 



Series B. — The four specimens of this seides differ from those 

 included in Series A in the relative flatness and narrowness of the 

 carapace, which has the antero-lateral borders less arched, so that 

 the lateral projection of the carapace bej'ond the exoibital tooth 

 is only about 2/3rds of the greatest diametei' of the orbit instead 

 of at least 5/6ths as in the larger specimens of Series A. These 

 differences, however, are rather less strongly marked in the 

 larger than in the smaller specimens of this series. The frontal 

 lobes are very prominent in one specimen, and in all there is a 

 tendency for the margin of the front to be less deflexed than in 

 Series A. The exorbital and epibranchial teeth are very pro- 

 minent, and, although the carapace as a whole is much less rough 

 than in the largest specimens of the first seiies, the epigastric and 

 postorbital crests are sharply defined and the oblique lines on the 

 lateral regions are niimerous, sharply cut, and granulated. The 

 mai-ginal granules on the nnder suiface of the merns of the 

 chelipeds are very prominent and spiniform. It is worth noting 

 that even in the larger of the two males the genital appendages 

 are very short, less than half the length of the abdomen, and 

 apparently immature. 



This form or variety seems to me to lead in the direction of 

 Hydrothelphusa. 



Series C. — The largest female in this series is only 16-25 mm. 

 in length, but is apparently adult ; the largest male is a trifle 

 larger. The carapace in all is rather convex, especially anteio- 

 posteriorly, and the front is bent downwards. The carapace, on 

 the whole, is rather wide, the ratio of breadth to length being, in 

 one specimen, as high as 1"37. The surface is rathei' smooth, 



