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Show 1900.] FROM 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. f. 5 (1873). Thalamita prymna, var. spinimana, Kossmann, Zoolog. Ergebn., Malacostr. pp. 47-49 (1877). Thalamita spinimana, de Man, Mergui Crust, p. 76, pi. iv. f. 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. d 70x43. d 59-5x37. d 48x30-5. d 59-5x37. $ 56x35. $54x33-5. 68. THALAMITA DAN^E 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. Five adult females, three with ova, and four young males. These are all of the variety stimpsoni, with rudimentary fourth antero-lateral tooth. Dim. $ 42x26. $ 27x17*5. $ 25-5x16-5. $ 21x12-5. $ 20x13. XLII. Genus POTAMON Sav. 69. POTAMON (PARATHELPHUSA) TRIDENTATUM INCERTUM, var. nov. (Plate XLVI. fig. 10.) For species cf. M.-Edw. Arch. Mus. t. vii. p. 171, pi. xiii. f. 1. (1854-55); Heller, 'Novara' Reise, Crust, p. 34 (1867); von Martens, Archiv fiir Naturgeschichte, pp. 18-22 (1868) ; Targioni- Tozzetti, 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 PROC. ZOOL. SOC.-1900, No. XLIX. 49 |