135 231 



The specimens taken in the Gulf of Siam vary considerably in regard to 

 colour-ornamentation. Some are quite white, others white with a few brown spots, 

 or with one or two broken-off brown rays, or with brown zigzag lines, etc. 



Circe lirata, Römer. 



{PI. IV, Figs. 28—31). 

 Venus (Circe) lirata, Römer, Monogr. d. Molluskengatt. Venus, I, 1869, p. 208, pi. .'ifl, fig. 2. 



Koh Kahdat, 1 fathom, sand (20). 



Long. 7 — 24 mm. 



Long. 24 mm., alt. 225 mm., crass. 11-5 mm. 



Distribution: — "Mare chinense" (Römer). 



The specimens from the Gulf of Siam correspond fairly well with Römer's 

 description ; the concentric, raised striæ are not so regular and prominent as shown 

 in Römer's figure. The individuals vary greatly in regard to the coloration, and 

 of the 20 specimens scarcely tWo are similar. The scale of colour graduates from 

 quite white, to white with a few small brown spots, or with brown rays, or with 

 larger scattered brown spots, to almost entirely brown. In individuals measuring 

 as much as 16 mm. the whole shell is seen to be covered with the peculiar radiating 

 sculpture which is characteristic of the species. The later growth of the shell 

 is smoother, especially towards the ventral side. The great prominence of the 

 umbonal region is very characteristic of this form. Gafrarium navigatum, Hedley, 

 from Mast Head Reef (Queensland),' is no doubt only a young individual of Circe 

 lirata, Römer, or another closely allied form. 



Circe nana, Melv. 



Circe nana, Melvill, Memoirs and Proc. of the Manchester Liter, and Philos. Soc., vol. 42, 1898, No. 4, 

 p. 31, pi. 2, fig. 9. 

 — — — Proc. Zool. Soc. London, 1906, p. 831. 



Between Koh Kut and Koh Kahdat, 10 fathoms, shells (Vs). "Gulf of Siam" (Vs). 



Long. 6 — 7'5 mm. 



Distribution:— Indian Ocean (long. 26M0' N., lat. 52° 50' E.). 



The figure which Melvill gives of this species shows but imperfectly the 

 beautiful sculpture which is produced by the fact that the grooves, which radiate from 

 the umbo, turn off on either side and cross the fine concentric liræ; but at the 

 middle of the valves only the concentric striation is usually present. 



Circe Melvilli n. sp. 



(PI. IV, Figs. 32-33). 

 This little species is roundly triangular in form, milky while, and rather 

 convex; the umbo is situated at about the middle, but in some specimens slightly 



1 Proc. Linnean Soc. New South Wales, vol. 31, 1906, p. 476, pi. 38, fig. 33. 



