1900.] ME. P. P. BEDFORD OK MALAYAN ECHINODEEMS. 285 



11. Lagakttm, sp. ? (Plate XXIII. figs. 7 «, b.) 

 Four small specimens were found among a number of individuals 

 of Laganum depressum and decagonale which I cannot ascribe to 

 either of these species. It seems possible that they may be hybrid 

 forms. The test is more swollen than in any specimens of either 

 of the two species named ; in shape they are quite orbicular and 

 the four genital pores are very large (the posterior being absent) ; 

 in the two smaller specimens the actinostome and anus are excep- 

 tionally large ; the internal calcareous connections between the 

 upper and lower surf aces are more complicated than in L. depressum. 

 but do not extend to half the distance from the periphery to the 

 centre as in normal L. decagonale (v. figs.). 



12. Aeachnoides placenta Agass. 



Arachnoides placenta, L. Agassiz, Monogr. d'Echinod. ii. 1841, 

 p. 94. 



Reference. Alexander Agassiz, Revision of Echini, pt. 3, 1873, 

 p. 530. 



Locality. Singapore, one specimen between tide-marks. 



Distribution. Mergui Archipelago, Burma, E. India Is., Aus- 

 tralia, and New Zealand. 



Transverse diameter 64 mm. Diameter in plane of odd ambu- 

 lacrum 65 mm. 



13. Echinodiscus l.evis Agass. 



Eehinodiscus Icevis, Alexander Agassiz, Revision of Echini, pt. 3, 

 1873, p. 533. 



Lobophora truncata, L. Agassiz, Monogr. d'Echinod. ii. 1841, 

 p. 66. 



Locality. Singapore, three specimens between tide-marks ; at 

 low tide they lie just covered by sand. 



Distribution. S. Africa, E. India Is., New Caledonia, China Seas, 

 and Japan. 



In one specimen the lunule is incompletely formed on one side, 

 the slit not being closed posteriorly ; in the others both lunulas 

 are complete. 



This species is very closely allied to E. biforis, from which it is 

 distinguished by the shape of the test, which is relatively longer in 

 the former, and the transverse line of greatest breadth passes close 

 to the apex, being much more anterior in position than in 

 E. biforis ; the lunules, also, are shorter. Louis Agassiz's dis- 

 tinction, based on the absence of transverse grooves between the 

 pore-pairs in L. truncata, does not hold good ; in one specimen the 

 pore-fields on the right side of the odd (ant.) ambulacrum aud 

 right posterior ambulacrum are devoid of continuous pore-grooves, 

 while on the other pore-fields they are present ; the characters 

 first mentioned are also so variable, that it is quite possible that 

 we are really dealing with a single species 1 . 



i Dr. Hanitsch has sent me an example of this species obtained at Malacca. 



