346 ROBERT TRACY JACKSON ON ECHINI. 



In the interambulacra of this choice specimen there are five columns of plates at the mid- 

 zone, in all five areas. Ventrally, there are two plates in the basicoronal row in all areas (Plate 

 43, figs. 1, 2), three plates in the second, and four plates in the third row. The fourth column 

 originates on the right of the center in areas A, C, and E; but on the left of the center in areas 

 G and I. In area A the fifth column originates as a pentagon in the sixth row, with a heptagon 

 on its right ventral border. In area I the fifth column originates also in the sixth row, but by 

 rare exception the initial plate is tetragonal, and to compensate for its two sides wanting, there 

 is a heptagonal plate, H, on its right ventral border and another on its left border. The inter- 

 ambulacral plates on the exterior (Plate 43, fig. 1), as usual, bear numerous small, secondary 

 tubercles. These tubercles are shown on the external mold (Plate 44, fig. 4), and especially 

 clearly on another external mold (Plate 44, fig. 5). 



The character of primary plates ventrally, passing into four columns dorsally, as seen from 

 the interior, is shown in Plate 39, fig. 6, and Plate 42, fig. 5. There is, however, some confusion 

 ventrally in area B, and the series is not so complete as in the cases previously described. 



*Lovenechinus anglicus sp. nov. 

 Plate 46, figs. 5, 6; Plate 47, figs. 3-5. 



^ Palacechinus yiyas Duncan, 1S89, p. 198, text-fig. i; Jackson, 1896, p. 204, Plalc 7, figs. 38, 39. 



^Non Pcdarchinus giqas M'Coy, 1844; non Baily, 1874, p. 41, Plate 3, figs, a-d; non Keeping, 1876. 



^Non PalacccJiinus gigas Loven, 1874, p. 41. 



^Non Maccoya gigas Pomel, 1883, p. 115; non Lambert and Thiery, 1910, \>. 11'.). 



' Palechinus gigns Tornquist, 1897, p. 739. 



' Pcdacchinus gigas (pars) Klein, 1904, p. 32. 



The specimen on which this species is based, in the Museum of Practical Geology Collec- 

 tion 6,576, is apparently that of which Professor Duncan figured the ambulacrum as Palae- 

 echinus gigas, and I also figured it as the same .species. The structure of the ambulacrum of 

 Palaeechinus gigas, however, is entirely different, being composed of primary and occluded 

 plates, all of which meet the middle of the half-area (Plate 47, figs. 1, 2). The great size of 

 the interambulacral plates, and also the original label, which reads Palaeechinus gigas, probably 

 misled Professor Duncan when he described it. 



This specimen is in many respects very perfectly jn-eserved, but is somewhat remarkable 

 for the peculiarities by which portions of the test are shown (Plate 46, fig. 5). In interambula- 

 crum A there are five columns of plates in place and a vacancy on the right for at least one 

 additional column, which would be a right pentagonal adradial. Ambulacrum B is represented 



' The several references included in these paragraphs are based on the .specimen here described as Lovenechinus anglicus 

 and which Duncan erroneously referred to Palaeechinus gigas, see )ip. 304, 321. 



^The several references included in these paragraphs refer to the true Palaechinus gigas of M'Coy, here referred to 

 Maccoya gigas, p. 321. 



