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have a rather well developed meshwork in the outer part of the blade. Tridentate 

 pedicellariæ have not been observed. The triphyUous pedicellariæ (PI. VII. Fig. 53) 

 are small and simple. ~ Sphæridiæ are found on the 4-5 lower plates. Spicules 

 have been met with only in the buccal membrane, and a few of the same shape 

 as those in the buccal membrane, in the walls of the genital organs. 



The spines (Fig. 7) are short, the longest about Vs — V4 of the diameter of 

 the test; they are rather robust, smooth, a little swollen at the point. Those around 

 the peri-stome are flattened at the end and curved. The smaller ones end in a 

 distinct central point with a circle of smaller points around; in the larger ones the 

 point is rounded (PI. II. Fig. 22). They are white with one or two narrow greenish 

 bands. Sometimes the base is reddish, and then the primary tubercles likewise 

 are reddish. 



The colour of the test is greenish with some irregular white spots. The 

 median naked part of the interambulacra on the abactinal side is mostly darker 

 coloured; there is thus formed a star-shaped figure on the abactinal side. A small 

 specimen of 3-5 mm. diameter has the interambulacra beautifully red, and in a 

 larger naked test (1Ü mm.) the Interambulacra are a little red at the ambitus. 

 These specimens otherwise agree completely with the rest. 



Koh Mesan, 3—15 fathoms (9 specimens); Koh Chuen, 15 — 38 faths. (7 spe- 

 cimens); Koh Kram, 20—30 faths. (2 specimens); Koh Kahdat, 10 faths. (1 specimen). 



This small species proves to be very widely distributed in the Indo-Pacific 

 Ocean. In the collections of the British Museum I have found some specimens 

 from the Seychelles, 12 fathoms (named Salmacis bicolore young), from Holothurian 

 Bank, North Australia, 15 fathoms (named Temnopleurus young) and from the Ami- 

 rante Islands, 17 fathoms (named Salmacis bicolor, young'.'), which I must refer to 

 PI. siamensis, in spite of some minor diflerences. A specimen from Torres Strait 

 (Haddon) found among some Echinids sent me for examination by Prof. S. F. 

 Harmer in Cambridge, must likewise be referred to this species. It is 12 mm. in 

 diameter, 8 mm. high, and is the largest specimen of this species that I have seen. 

 (PI. I. Figs. 7, 11. PI. II. Figs. 2, 9, 14.) Also the „Siboga"-Expedition has dredged 

 several specimens of this species. --- Seeing from de Meuere's remarks on 

 Pleurech. bothnjoides („Siboga"-Ech. j). 77) that probably more than one species had 

 been included under this name, I asked Dr. de Meijere to let me see the speci- 

 mens, and he most kindly sent me all of them. As supposed, I found them to be- 

 long to several species, viz. PL maculatus (described below), siamensis and scillæ, 

 besides the true bothryoides. The species siamensis was found to occur in many of 

 the stations (enumerated on p. 202 of the „Siboga"-Echinoidea), being thus very 

 common in the Malay Archipelago. 



AH these specimens show the species to be very variable. Several of the 

 specimens from „Siboga" are quite like those from the Gulf of Siam; others are 

 much darker, brownish with white spots or quite brown. The specimens from the 



Ü. K. U. Vidensk. Selsk. Ski-., 7. Kække, naturviüenäk. ug luutlieni. At'ü. 1. 1. 



11 



