MACCOYA. 319 



(1865c, p. 89) this is the probable locality of the holotype which is in the collections of Trinity 

 College, Dublin; County Kildare, Ireland, British Museum Collection E 3,652; Waterford, 

 County Wexford, Ireland, British Museum Collection E 361; Clitheroe, Lancashire, British 

 Museum Collection E 4,353; Clitheroe, Lancashire, Sedgwick Museum, Cambridge, Collection 

 17; Hook Head, County Wexford, Ireland, Sedgwick Museum Collect ion nos. land 5; Whatley, 

 near Frome, Somerset, Strassburg Museum; East Hum, northeast of Stewarton, Scotland 

 (Smith). 



Taking up the specimens attributed to Maccoya sphacrica, a specimen in the British 

 Museum Collection E 3,652, is from Kildare, and is free from matrix, but not very clearly pre- 

 served. It measures about 50 mm. in height and 52 mm. in diameter. The ambulacra are 

 narrow, about 6 mm. in width at the mid-zone. The interambulacra are about 26 mm. in widt h. 

 The ambulacral areas are rounded outwardly as in the type, but details of plates are obscure. 

 Pore-pairs are alternate and plates are apparently alternately primary and occluded. In the 

 only good interambulacral area there are seven columns of plates at the mid-zone. This speci- 

 men in structural detail resembles M'Coy's type more closely than any other specimen I have 

 seen. It also resembles it very closely lithologically, which lends weight to Baily's statement 

 that the type is probably from Kildare, which is the source of this individual. 



In the British Museum Collection E 361, is a limestone slab from Waterford, Ireland, 

 which bears two specimens, one of which is one of the finest of known Palaeozoic Echini. The 

 slab measures 200 mm. long by 125 mm. in width. The more nearly perfect specimen is shown 

 in Plate 32, fig. 4, and Plate 34, figs. 4-6. The test is spheroidal, somewhat crushed laterally. 

 The ambulacra at the mid-zone measure about 7 mm., the interambulacra 25 mm. in width. 

 From these measurements the circumference would be about 160 mm. and the diameter about 

 50 mm. Ambulacral areas are narrow, with two columns of low plates in each area. All 

 plates meet the middle of the area, and at the mid-zone most of the plates reach the inter- 

 ambulacra, but alternately they are widened and narrowed marginally, the narrowed plates 

 being nearly or occasionally quite excluded from contact with the interambulacrum. A few 

 completely occluded plates occur in each of these specimens, though none is shown in Plate 

 34, fig. 4, the ambulacra in which are drawn somewhat diagrammatically with certain oversights. 

 It was this specimen on which Professor Duncan (1889, p. 200, text-figs, ii-vii) based his ob- 

 servations of the structure of the ambulacrum in this species. In his text-figs, vi, vii, small 

 demi-plates are shown which he letters as a. These plates, having been overlooked, are not 

 shown in my figures, but nine such plates were counted in the best specimen (Plate 32, fig. 4). 

 Such plates are not a character of this species or genus, and are to be considered as excep- 

 tional progressive variants. At the mid-zone the pore-pairs are biserial, the outer pore of one 

 plate being about in line with the inner pore of the next succeeding plate. Dorsally, near the 

 oculars, as a localized stage, all plates are of equal height, meet the interambulacra fully, and 



