416 ROBERT TRACY JACKSON ON ECHINI. 



Twelve columns of plates in an ambulacral area and six columns of plates in an interambulacral area; 

 ambulacral areas elevated as prominent ribs L. carinata sp. nov., p. 424. 



Sixteen columns of plates in each ambulacral area and four (exceptionally five) columns of plates in each 

 interambulacral area; ambulacra about twice as wide as the interambulacra . . L. colletti White, p. 425. 



Sixteen columns of plates in an ambulacral area and four columns of plates in each interambulacral area; 

 ambulacral areas several times as wide as the interambulacral . . . . L. extremis sp. nov., p. 430. 



Number of columns of ambulacral and interambulacral plates in an area unknown; ambulacral plates 

 proportionately lower and wider than in any other known species of the genus L. caledonica sp. nov., p. 432. 



*Lepidesthes wortheni Jackson. 

 Plate 66, figs. 1-3; Plate 67, figs. 8-14. 



Lepidesthes wortheni Jackson, 1896, pp. 207, 241, Plate 9, fig. 53; Klem, 1904, p. 26; Lambert and Thiery, 

 1910, p. 123. 



Test elliptical. The type (Plate 66, fig. 3) is a small individual and measures about 36 mm. 

 in height and 27 mm. in width, but it is incomplete laterally, and the diameter, if complete, 

 would be somewhat greater, probably about 30 mm. The ambulacra at the mid-zone measure 

 9 mm. in width and the interambulacra from 5 to 6 mm. in width. A large and nearly perfect 

 specimen in Mr. Braun's collection (Plate 66, fig. 1) measures about 60 mm. in height and 55 

 mm. in width through the mid-zone. The ambulacra at the mid-zone measure 15 mm. in 

 width and the interambulacra 9 mm. in width. 



The ambulacra are wide, with eight columns of plates at the mid-zone. The plates are 

 nearly or quite rhombic in young specimens (Plate 67, fig. 9), but are hexagonal in larger speci- 

 mens (Plate 67, fig. 8). Ventrally, near the peristome there are four columns of plates only, in 

 this character being like the ventral border of Melonechinus (Plate 56, fig. 3). The pores are 

 surrounded by peripodia, and are situated above the middle and nearer the outer border than 

 the median line of each plate, so that from the median line they are situated toward the next 

 adjacent interambulacrum on either side (Plate 67, figs. 8, 10). In small specimens the pores 

 lie nearer the middle line of each plate (Plate 67, fig. 9). The ambulacral plates bear numerous 

 secondary tubercles; they imbricate adorally, and laterally bevel strongly under the adradials. 



The interambulacra are narrow, -with, at the mid-zone, three columns of plates which 

 are rounded on the suture lines. The plates imbricate strongly aborally, and the plates of 

 the central column imbricate strongly laterally over the plates of the two adradial columns, 

 and these in turn over the ambulacrals on the adradial sutures (Plate 67, fig. 8). The inter- 

 ambulacral plates bear numerous secondary tubercles and spines, which are slender, swollen 

 at the base, and vertically finely striate (Plate 67, figs. 13, 14). At the ventral portion of the 

 interambulacrum, as far adorally as preserved, there is a row of three plates (Plate 67, fig. 8). 

 Above this row a fourth column is introduced with a pentagonal plate, but there are only four 



