MACCOYA. 323 



meet and are cut off from interambulacral contact (Plate 47, fig. 1); pore-pairs are biserial, as 

 in M'Coy's type. The ambulacral plates bevel strongly over the adradial.s laterally. Adradial 

 plates on the inclined marginal face show one set of facets distally for articulation with the 

 primary ambulacral plates, but, passing proximally on the inclined face, these facets become 

 narrower and other facets appear between them, so that proximally there are facets for each 

 ambulacral plate of the area, as explained in detail in the case of Maccoya intermedia (p. 315, 

 Plate 34, figs. 2, 3). The adradial plates of this specimen measure 8 mm. in width and the same 

 in height, hexagonal plates 10 mm. in width and 8 mm. in height. Another specimen from 

 Rahan's Bay, in the Sedgwick Museum, no. 260, consists of two large hexagonal interambu- 

 lacral plates with good tubercles. The larger of these plates measures 12 nun. in width, 9 

 mm. in height. The size and locality indicate that it belongs to this species. 



*Maccoya gracilis (Meek and Worthen). 

 Plate 34, figs. 11, 12; Plate 35, figs. 1-3. 



Palaechinw gracilis Meek and Worthen, 1869, p. 82; 1873, p. 473, Plate 10, fig. 2; Keyes, 1895, p. 180. 



Palaeechinus gracilis Loven, 1874, p. 41; Duncan, 1889, p. 205. 



Maccoya gracilis Pomel, 1883, p. 115; Lambert and Thiery, 1910, p. 120. 



Rhoechinw gracilis Jackson, 1896, p. 201, Plate 7, figs. 36, 37; Tornquist, 1897, p. 762; Klem, 1904, p. 29. 



The test is small, high, spheroidal. In the holotype (Plate 35, fig. 1), the width of the 

 ambulacrum at the mid-zone is 5.5 mm. ; width of the interambulacrum about 19.5 mm. From 

 these measurements the circumference would be about 130 mm. and the diameter about 41 mm. 

 The ambulacra are narrow, composed of two columns of plates, all of which meet the middle of 

 the area, but on the margin alternate plates are primaries, meeting and enlarged at the inter- 

 ambulacral contact; the plates between are occluded, marginally narrowed and nearly or quite 

 cut off from interambulacral contact by the enlargement of their fellows. Pore-pairs biserial, 

 the outer pore of the inner pair about in line with the inner pore of the outer* pair. 



I nter ambulacra are wide, in the holotype (Plate 34, fig. 11) with seven columns of plates 

 at the mid-zone in the only area that is at all complete in this specimen. The adambulacral 

 plates are pentagonal and those of intermediate columns hexagonal. Dorsally, the seventh 

 column is interrupted, there being one row of six plates built, above which the seventh column 

 appears again, with a pentagonal plate having a heptagon lying on its left lower border. Am- 

 bulacral and interambulacral plates alike bear small secondary tubercles. 



Another specimen from Burlington in the Museum of Comparative Zoology (3,009) is a 

 larger individual, but fragmentary and represented by an internal impression. There are six 

 columns of interambulacral plates at the mid-zone. This specimen was incorrectly referred to 

 burlingtonensis by me (Jackson, 1896, p. 204), as I was misled by the original label which bore 

 that name. 



