PLATE 76. 



Meekechinus elegans sp. nov. Page 443. 



Figs. 1-4, 6. Same specimen as photograph, Plate 75, fig. 6. Holotype. 



Fin. ' Dorsal view of the test of this remarkable echinoid. X 2.7. Ambulacra very broad, with 20 columns of plates 

 in eai-li art\i near (lie mid-zone, seen best in the right half of area IV, where ten plates may be counted from the center 

 outward in a half-area. Ambulacral plates are all low, wide rhombs; pore-pairs are in peripodia in that portion of 

 each plate nearest to the next adjacent interambulaerum. Ambulacral plates imbricate strongly ventrally and 

 laterally bevel under the adambulacrals. Interambulacra very narrow, each composed of three columns of small 

 plates, which arc uniform in. size, imbricating strongly dorsally and from the center laterally and over the ambulacra 

 on the adradial suture. Each plate typically with a small primary and secondary tubercles; occasionally and with- 

 out apparent rule, a plate of the middle column may fail to develop a larger tubercle. Three small oculars and five 

 genitals are preserved ; a large madreporite with fine pores and many small tubercles is a prominent feature (more 

 enlarged in fig. 6). 



Tig. 2. Ambulacral plates-from the mid-zone of area I, from the place marked X in fig. 1, showing ventral imbrication. 

 X 5.3. Pore-pairs are in peripodia in the left of the plate on the left of the median line and in the right portion of 

 the plate on the right of the median line; there are small primary tubercles with a scrobicule and secondary tubercles 

 on each plate, the only case of such a structure of ambulacral plates known in the Palaeozoic. Small primary and 

 secondary spines are present. 



Kit;. 3. Similar ambulacral plates, from the right half of the mid-dorsal region of area III from the place marked X in fig. 1. 

 X 5.4. The aboral beveled edges are very marked; two of the plates are seen from the interior, with pores in the 

 middle of each plate instead of near the lateral border of plate, as on the exterior. 



Fi'.i. 4. Segment of an interambulaerum, at the mid-zone of area 3 from the point marked X in fig. 1. X 5.2. The plates 

 of column 3 imbricate strongly dorsally and from the center laterally and over the ambulacrals on either side. A 

 small perforate primary tubercle with scrobicule is in the center of each plate, with, in addition, rather large 

 secondary tubercles. Three typical primary and a secondary spine are drawn separately. 



Fig. 5. Segment of interambulaerum. Same specimen as photograph, Plate 75, fig. 7, paratype. Drawn from a point 

 halfway between the ambitus and the apical disc in area 2. All interambulacral plates imbricate strongly dorsally 

 and from the center laterally and over the ambulacra on the adradial suture. The middle plate of the upper row 

 has no primary tubercle as have the others. 



Fig. 6. Apical region. X 5.3. The plates in some parts are disarranged, but in others are apparently in their original 

 relation. Oculars II and III are in place, exsert, and small, but adorally cover the ambulacra and laterally the 

 interambulacra in part on either side. Apparently there is an ocular, oc., in area V, but one cannot ascertain an ocular 

 with assurance in areas IV or I. The madreporite is very large, with numerous fine madreporic pores, and in addition 

 two genital pores, also many secondary, but no primary tubercles. Genitals 1, 3, and 4 are small plates each with a 

 primary and secondary tubercles and four genital pores; genital 5 is similar, but with three pores. The ambulacra 

 dorsally have only one plate in contact with the ocular, but the absence of a second plate is probably due to displace- 

 ment during fossilization in the slipping of strongly imbricating plates. A few plates in the center may be considered 

 as periproctal. 



Fig. 7. Same specimen as photograph, Plate 75, fig. 8. Paratype. X 5.3. A nearly complete lantern. Pyramids are 

 wide-angled, with a rather deep foramen magnum, seen best in area E. In area A the side wing of the left half- 

 pyramid shows ridges for the attachment of the interpyramidal muscle. In area C, a tooth is in place, seen for 

 nearly its whole length on account of the accidental separation of the half-pyramids on their suture line. The 

 tooth is vertically striate, and distally dentate, the same structure being seen also in the tooth of area A. The 

 left half-pyramid of area E shows the suture line for the epiphysis which is wanting, but the right half-pyramid of 

 C has the epiphysis, ep., in place, against which lies a somewhat displaced brace, 6. A bifid compass, c, lies out of 

 place below the pyramid E (p. 181). 



Figs. 8, 9. The same specimen as Plate 75, fig. 7. Paratype. Tridentate pedicellariae. X 62. These are quite like 

 t ho pedicellariae of modern Echini, and are the first recorded from the Palaeozoic and indeed are the first found 

 fossil from any formation as far as I am aware excepting in the Jurassic Pelanechinus in which they are described by 

 Groom (1887), (p. 61). 



