308 ROBERT TRACY JACKSON ON ECHINI. 



are primaries, meeting the middle of the area and the interambulacral areas. The pore-pairs 

 are uniserial (Plate 30, fig. 10). M'Coy was quite correct in describing the ambulacral struc- 

 ture as he did, and Duncan (1889, p. 200, text-fig, viii) was mistaken when he claimed for 

 this species the structure of four columns of ambulacral plates and a biserial arrangement of 

 pores in an area. Duncan's specimen is in the Museum of Practical Geology Collection 16,301 ; 

 it has no connection with Palaeechinus ellipticus, and is here described as Lovenechinus lacazei 

 (footnote p. 303; p. 329, Plate 36, figs. 1-3). 



The interambulacrum of ellipticus has five columns of plates at the mid-zone, as shown in 

 two areas of the type; the adambulacral plates are pentagonal, the others hexagonal. In 

 one area (Plate 30, fig. 8) there are two plates in the basicoronal row, three in the second, four 

 in the third, and five in the fifth row. Ambulacral and interambulacral plates alike have 

 numerous secondary tubercles. The holotype is the only specimen of the species known to me, 

 and the numerous figures in text-books are taken from M'Coy's original figures, since when it 

 has not been published from direct observations. This species is the type of the genus as 

 selected by Lambert and Thiery (1910, p. 119). 



Lower Carboniferous, Millicent, County Clare, Ireland; holotype in the Griffith Col- 

 lection, Science and Arts Museum, Dublin; a cast of this specimen is in the Museum of 

 Comparative Zoology Collection 3,115. 



The specimen referred to Palaeechinus ellipticus by Baily (1865a, 1865c) and by Quenstedt 

 who copied Baily's figure, has four columns of interambulacral plates, and is here referred 

 to Palaeechinus quadriserialis. The specimen referred to P. ellipticus by Duncan (1889, p. 

 200) is here referred to Lovenechinus lacazei (p. 329) as above stated. 



*Palaeechinus elegans M'Coy. 

 Text-figs. 9, p. 54; 15, p. 59; 237, p. 231; Plate 29, figs. 3, 4, 6; Plate 30, fig. 11; Plate 31, figs. 1-5. 



PalaecUnus elegans M'Coy, 1844, p. 172, Plate 24, figs. 2a-2d; Roemer, 1852-'54, p. 287, Plate 4, figs. 



la-Id; Desor, 1858, p. 158; Baily, 1865, pp. 44, 45; 1865b, pp. 63-65, and 67, Plate 4, figs. A-E; 



Quenstedt, 1875, p. 380, Plate 75, figs. 39, 43; Baily, 1875, p. Ixviii, Plate 36, figs. 1 la-lid; A. Agassiz, 



1892, p. 73, Plate 29, fig. 2; Tornquist, 1893, p. 103; Lambert and Thiery, 1910, p. 119. 

 Palaeechinus elegans Loven, 1874, p. 41. 

 Palaechinus [elegans] Etheridge, 1874, p. 311, Plate 3, fig. 3. 

 Rhoechinus elugans Duncan, 1889, p. 205; Jackson, 1896, table facing p. 242 (but not text-fig.l, p. 205, 



and not Plate 7, fig. 40 1 ); Tornquist, 1897, p. 757, Plate 21, figs. 6, 7; Klem, 1904, p. 28; Fraipont, 



1904, p. 10, Plate 2, fig. 9. 



I had the opportunity to study M'Coy's type of this species and also other good specimens 

 as described in some detail below; from all of these the species description is made up. Test 



1 These figures are referable to Maccoya intermedia, see p. 314. 



