LEPIDESTHES. 429 



Dorsally, near the oculars, there are few, even two plates in one row in an area, and the number of 

 columns increases, passing ventrally, as above described. In the interambulacral areas all four 

 columns continue to the apical disc. In four areas, coluimi 3 consists of wide plates imbricating 

 laterally in two directions, and in these areas' there is one column on the left, and two on the 

 right of this wider column. In one area, 4, column 4 consists of wide plates with two columns 

 on the left and one on the right. The apical disc and periproct are well preserved as above 

 described. 



A specimen in Mr. Braun's collection (Plate 69, fig. 5) is like that just described, a dorsal 

 view and very well preserved. The ambulacral plates are all rhombic. In the interambulacral 

 areas A and E, column 4 is the wider column, and in C and G, 3 is the wider column; area I is 

 doubtful, but apparently column 3 is composed of wide plates. Periproctal plates, similar to 

 those of text-fig. 251, are in place, but the plates of the apical disc were not worked out. 



A choice specimen in the Museum of Comparative Zoology is perfect in form from the 

 mid-zone up, but ventrally is somewhat imperfect (Plate 69, fig. 6; Plate 70, fig. 1). The am- 

 bulacral plates are for the most part rhombic, but a few at the mid-zone and ventrally have 

 their dorsal and ventral borders more or less completely truncated, forming hexagons. The 

 interambulacral areas are complete, and in both areas A and C, column 3 consists of broad 

 plates imbricating laterally in two directions over the plates of the adjacent columns. Ventrally, 

 the tips of dental pyramids are in place. 



A specimen which I gave to the British Museum, and now no. E 10,677 of that collection, is 

 similar to the one just described, but somewhat smaller. It is laterally compressed, and measures 

 39 mm. in height and 34 mm. in width. The ambulacra measure 13 mm. in width and the 

 interambulacra about 5.5 mm. in width. Ambulacral plates are rhombic, with 16 columns in 

 an area at the mid-zone. The interambulacral areas are not very clearly preserved, but there 

 are four columns in two areas. In area A the plates of column 3 are wider, imbricating 

 laterally in two directions, and in area C the plates of column 4 are wider. The tips of five dental 

 pyramids with traces of teeth are seen ventrally. 



A very large and well preserved specimen in the Museum of Comparative Zoology shows 

 many interesting characters (Plate 69, fig. 7; Plate 70, figs. 3, 4). This specimen measures 

 70 mm. in height and about 61 mm. in width. The ambulacra are about 24 mm., and the 

 interambulacra about 10 mm. in width. The ambulacra at the mid-zone are relatively wide 

 hexagons, the dorsal and ventral border of each plate impinging on and truncating ventrallj^ 

 or truncated dorsally by, the next succeeding plate of its own series. This is quite distinct 

 from the rhombic plates seen at the same area in younger specimens (Plate 71, fig. 1). Dorsally, 

 however, a different condition exists, for in this region, as seen in the middle line of area J 

 (Plate 69, fig. 7), the ambulacral plates are rhombic in shape, therefore in a large individual, as a 

 localized stage, these younger plates have the character of all the plates of a younger individual. 



