188B.] FROM TUTICORIN, MADRAS. 385 



V. HOLOTHUROIDEA. 



38. Haplodactyla australis, Semp. 



39. Holothiiria atra, Jdger. 



40. marmorata, Jdger. 



41. Holotburia monacaria, Lesson. 



42. vagabunda, Selenka. 



Notes and Descriptions. 



Oreaster thurstoni. 



A triplacanthid form, with the spines, except the five apicals, as 

 a rule poorly developed. 



R=2'7 r. Disk moderately elevated; lophial spines only just 

 indicated ; a spinous tubercle on both supero- and int'ero-marginal 

 plates, very rarely more than one ; no spines on the ventral plates. 

 The arms rather short, wide at their base ; marginals about twenty, 

 both above and below ; angles between the superoinarginals, into 

 which the pores extend. The spinous tubercles are very slight, and 

 present no indication of becoming spines. 



Adambulacral spinulation triplacanthid ; spines of innermost row 

 eight in number, diverging very gracefully, not very slender ; in the 

 middle and outer rows there are two or three spines in each cluster, 

 and these are, as usual, much stouter ; but the middle row is much 

 more prominent than the outer. The granulation of the lower 

 surface tends to take on a regular pattern, owing to the aggregation 

 of the grannies into tufts, in the centre of which is a spiniform 

 tubercle. There is a plentiful supply of sessile bivalved pedicellariae. 

 The pore-areas of the dorsal surface are very distinctly marked on 

 and near the disk, but are rather vaguer near the sides of the arms ; 

 there is no central apical spine ; the five spines which end the 

 lophial line are large and prominent, and have a marked tendency to 

 double ; the other spines of the lophial line are very inconspicuous. 

 Along either side of that line there runs a row of small tubercles ; 

 outside these there is another row which does not extend beyond the 

 disk ; the constituents of these rows are quite small and incon- 

 spicuous. Madreporic tubercle large, just outside apical region, 

 irregularly quadrate. Colour creamy yellow. R=130, r=A7 

 millim. 



Of the five specimens which I refer to this species three have the 

 characters just enumerated ; the two other examples differ to a 

 somewhat remarkable extent from what appears to be the more 

 typical form of the species. In one the apical spines are much less 

 prominent than in the form already described, while the tubercles 

 on either side are much more distinctly spinose, and many of the 

 infero-marginal plates have several spinous tubercles in a tuft. In 

 the other specimen the apical spines remain large, while the 

 tubercles on either side become quite prominent, and the whole 

 appearance of the form is thereby quite altered. 



By many zoologists these three forms would be regarded as three 

 distinct species ; but I do not think that anybody who knows how 

 Echinoderms vary will regard them as anything else than varieties 

 of one and the same species. However, there are, in this instance, 



