ECHINODEEMATA. 145 



by the fact that two successive plates are so marked, and that then 

 there is an interval of two or more not so distinguished. Three or 

 four blackish dots are to be found on the radial shields, along the 

 line of the vertical side ; by pairs or threes the upper arm-plates are 

 faint pink or light green, and the pink ones are distinguished by 

 each having a black dot. 



I have taken advantage of the locality of this well-marked and 

 really beautiful species to associate with it a name honoured by 

 us all. 



Port Darwin, 7-12 fms., mud and sand. 



24. OpMothrix melajiogramma. 



Disk pentagonal in appearance, completely covered with fine 

 spinules, which are a good deal longer and rarer on the actinal sur- 

 face. Arms 4-5 times the diameter of the disk, taperiag very deli- 

 cately ; the upper surface marked by a black line, which extends a 

 good way on to, but does not reach, the centre of the disk. 



The radial shields are almost completely obscured by the spinu- 

 lation, which is very delicate ; mouth-shields broader than long, the 

 inner sides meeting at an acute angle, the outer edge rather evenly 

 rounded, the bridge between the genital slits very narrow ; seven or 

 eight arm-spines, the two lowest very small, the upper one as long 

 as five or six upper arms-plates, but the uppermost of all is ,not the 

 longest ; the upper spines are richly and delicately echinulated, and, 

 owing to the great encroachment of the side arm-plates on the upper 

 surface of the arm, the spines of either side come to lie very close to 

 one another, and soon obscure the arm itself. One small tentacle- 

 scale. The lower arm-plates have a concave notch on their adoral 

 edge, have a short side passing into the short lateral edge, and are 

 three-sided on their aboral face, so that they form an irregular 

 hexagon which is broader than long. Owing to the size of the side 

 arm-plates, the upper arm-plates are lozenge-shaped. 



This species has a most elegant appearance, the black band already 

 spoken of relieving the whiteness of all the other parts, while a kind 

 of feathery appearance is given to the arms by the delicate plates 

 and long glassy spiaes. 

 Prince of Wales Channel. 



25. OpMomaza cacaotica. 

 Lyman, p. 37. 



The coloration of these specimens is very far from the chocolate 

 of Mr. Lyman's type ; but three specimens coUeoted in one locality 

 (Gulf of Suez) are — one chocolate-colouired, one quite light, and one 

 intermediate. A discussion, however, of the characters of the 

 variations of this species wiU be more profitable when our series is 

 larger. 



Port MoUe ; Prince of Wales Channel. 



