MUSEUM OF COMPARATIVE ZOOLOGY. 049 



Teeth : tooth-papilla^ and mouth-papilla? sharp, slender, spiniform ; those 

 standing in the place of teeth are about nine, arranged partly in a single, 

 partly in a double vertical row; the longest 1.5 mm. Those near the outer 

 corner of the mouth-slit are smaller, stouter proportionately, and irregularly 

 crowded; length not over .5 mm. One madreporic shield, like a small 

 pimple, about 2 mm. long, placed in a depression near the inner angle of the 

 interbrachial space. Top and sides of arms, down to the tentacle scales, 

 covered with a smooth mosaic of flat, irregular, rounded grains. Lower 

 surface of arm, between the tentacle pores, smooth. Skin of the lower surface 

 of the disk studded with flat, smooth grains, somewhat rounded; from six to 

 nine to a square mm. but not confluent so as to form a mosaic. The space 

 between the upper and lower surfaces of the disk is quite concave and very 

 distinct, its skin being nearly naked and only covered by scattered micro- 

 scopic grains. Whole upper surface of disk covered with a mosaic of grains 

 like that of the arms ; in addition to which the high radial ribs and the 

 round space enclosed by the inner ends of the ribs, bear stout, smooth, conical 

 spines, the largest 1.5 mm. high ; of these there are ten or twelve to each 

 rib, arranged in an irregular double row; those in the centre of the disk are 

 crowded and smaller ; the same spines form a row along the top of the arm, 

 as far as the third fork ; they'are smaller than those of the disk, and there is 

 usually one to each joint. Toward the end of arm each joint is marked by 

 an annular ridge, which consists of a double row of grains, each bearing a mi- 



