LEPIDESTHES. 419 



Test small, spheroidal or slightly ellipsoidal. The holotype (Plate 66, figs. 4, 5), as esti- 

 mated by restoring the ventral portion, measures about 33 mm. in height. The ambulacra 

 at the mid-zone are 12 mm. in width and the interanibulacra 7 mm. in width. From these 

 measurements the circumference would be about 95 mm. and the diameter about 30 mm. This 

 represents practically a full grown individual, none of the specimens seen being essentially, if 

 at all, larger. 



The ambulacra are wide, nearly twice as wide as the interambulacra, with, at the mid-zone, 

 eight columns of small, nearly rhombic plates in each area (Plate 68, fig. 4). The plates im- 

 bricate adorally and laterally bevel under the adradials. The pore-pairs lie slightly above the 

 middle of each plate, and either in the median line or a little nearer to the next adjacent inter- 

 ambulacrum. Ventrally, there are four columns of ambulacral plates near the peristomal 

 border, as seen in area B of Plate 68, fig. 3. In other areas of this figure there appear to be 

 fewer columns, but the ambulacral plates are more or less confused and the number of columns 

 cannot be ascertained with assurance. From this zone of four columns the number increases 

 rapidly to the full complement of eight columns, as seen in the aboral portion of ambulacrum B 

 in this figure. Dorsally, next to the ocular plate, in the placogenous zone, there are few plates 

 and apparently only one against the ocular, but one is such an unnatural number for an am- 

 bulacrum that there is probably some plate pushed under, or otherwise obscured. From this 

 small number dorsally, the number of columns increases rapidly, passing ventrally, until the 

 full number is attained. My figures of the type (Plate 68, figs. 4, 5) are so much enlarged that 

 I could not include the whole specimen, but this is compensated for by the photographic figures 

 (Plate 66, figs. 4, 5) and by Miller's excellent figure of the whole specimen. 



The interambulacra are nari-ow at the mid-zone, with in each area five columns of plates 

 which are small, rounded on the suture line, and imbricate strongly aborally and from the center 

 outward and over the ambulacrals. Ventrally the primordial interambulacral plate is appar- 

 ently in the basicoronal row (Plate 68, fig. 3), with two plates in the second row, three in the 

 third, and four in the fourth row. The point of origin of the fifth column was not definitely 

 ascertained, but it is below the mid-zone, and in the type (Plate 66, fig. 4) there are five columns 

 as far ventrally as the area can be traced. Dorsally the interambulacral plates impinge upon 

 the oculars broadly on either side. 



The peristome is covered with ambulacral plates onlj- (Plate 68, fig. 3), and this figure 

 represents the best peristomal area known in the family. Teeth are visible in the center of 

 the area. Dorsally in the type, a number of ocular and genital plates are in place (Plate 68, 

 fig. 5). The oculars are relatively large and separate the genitals, meeting the periproct, as 

 usual in the Palaeozoic. Two of the oculars have two pores. This is a very exceptional fact, 

 as pores in ocular plates are very rare in Palaeozoic Echini, and no other case of two pores is defi- 

 nitely known (pp. 89, 413, 435). It is true that Bail}' described two pores in ocular plates of 



