476 



H. MATSUMOTO 



Diameter of disk 6.5 mm. Length of arm 25 mm. Width of arm 

 at base 1.5 mm. 



Disk five-lobed, with indented interbrachial borders. Dorsal surface 

 of disk covered with granules and rounded convex plates of unequal 



size. The plates are coarser and 

 more close-set along the radii and 

 interradii, where the granules are not 

 so numerous as to form belts around 

 the plates. The more convex ones 

 of the plates are nearly hemispheri- 

 cal. The radial and interradial parts 

 covered by these plates are more 

 elevated than the surrounding parts 

 covered with the granules ; so that, 

 the dorsal surface of the disk pre- 

 sents ten radiating ridges alternating 

 )' with ten radiating furrows. Radial 

 shields partly naked ; the naked 

 parts are pear-seed shaped or irre- 

 gularly oval, rather unequal in size, 

 one third to two fifths as long as the 

 disk radius, about twice as long as 

 wide, widely separated from each 

 other. 



Interbrachial ventral surfaces covered with granules similar to those 

 of the dorsal side, but without plates. Genital slits very small, short, 

 situated at the inner, adradial corners of the interbrachial ventral 

 surfaces ; those of the same interradius diverging outwards. The areas 

 j.ust inside the interbrachial ventral surfaces are covered with a pave- 

 ment of coarse, polygonal or rounded, flattened grains of unequal size, 

 and mingled among them are a number of coarse, hemispherical tuber- 

 cles. A single madreporic shield, situated at the inner angle of an 



Fig. 1. 



Astrothrombus chrysanthi, sp. nov. x 8. 

 a. From above. b. From below. 

 c. Lateral view of three arm joints near disk. 



