1900.] EBOM SINGAPORE AND .MALACCA. 749 



67. Thalamita spinimana Dana. 



Thalamita spinimana, Dana, U.S. Expl. Exped., Crust, p. 283, 

 pi. xvii. f. 8 (1852); A. M.-Edw. Nouv. Arch. Mus. t. ix. p. 165, 

 pi. iv. £. 5 (1873). 



Thalamita prymna, var. spinimana, Kossmann, Zoolog. Ergebn., 

 Malacostr. pp. 47-49 (1877). 



Thalamita spinimana, de Man, Mergui Crust, p. 76, pi. iv. £. 7 

 (1888). 



Hab. Singapore ; from a shoal exposed at low water. Four 

 males and two females. The approximation of the median lobes 

 of the front varies, from a state of almost complete fusion in the 

 smallest to a separation of quite a millimetre in the largest. In 

 one female the median and submedian frontal lobes are partially 

 fused. 



Dim. s 70x43. s 59-5x37. 6 48x30-5. 6 59-5x37. 

 ? 56x35. $54x33-5. 



68. Thalamita hajsm Stimpson. 



Thalamita crenata, Dana, U.S. Expl. Exped. pt. i. p. 282, 

 pi. xvii. f. 7 (1852). 



Thalamita dance, Stimpson, Proc. Ac. Nat. Sci. Philad. p. 37 

 (1858); A. M.-Edw. Arch. Mus. t. x. p. 366, pi. xxx. f. 1 (1861). 



Thalamita stimpsoni, A. M.-Edw. t. c. p. 362, pi. xxxv. f. 4. 



Thalamita dance, de Man, Mergui Crust, p. 78 (1888). 



Hab. Singapore ; littoral. Eive adult females, three with ova, 

 and four young males. These are all of the variety stimpsoni, 

 with rudimentary fourth antero-lateral tooth. 



Dim. $ 42 x 26. $ 27 x 17-5. $ 25-5 x 16-5. $ 21 x 12-5. 

 ? 20x13. 



XLII. Genus Potamon Sav. 



69. Potamon (Pabathelphusa) tbidentatum incebttjm, var. 

 nov. (PlateXLVI. fig. 10.) 



For species cf. M.-Edw. Arch. Mus. t. vii. p. 171, pi. xiii. f. 1. 

 (1854-55); Heller, ' Novara ' Eeise, Crust, p. 34 (1867); von 

 Martens, Archiv fur Naturgeschichte, pp. 18-22 (1868) ; Targioni- 

 Tosszetti, Zoologia del viaggio della Magenta, Crostacei, p. 93, 

 pi. vi. f. 4 (1877) ; de Man, Notes Leyd. Mus. vol. xxi. nos. i.-iii. 

 pp. 67-70 (1899). 



Hab. Singapore ; from a lake in the Botanical Gardens. Three 

 males and two females, ranging from 17 mm. to 39-5 mm. in the 

 length of the carapace. 



The most notable point in this well-marked variety is the 

 structure of the inner and under angle of the eyes. The lower of 

 the two teeth described by M.-Edw. as occurring in this position 

 is well developed, and agrees entirely with his description and figure, 

 but the upper tooth is not all prominent, though still represented 

 by a very small lobe, occupying the same position and abutting on 



Pboc, Zool. Soc — 1900," No. XLIX. 49 



