PALAEECHINUS. 307 



plate that impinges on the initial plate of column 3, and in virtue of its one side lacking, a com- 

 pensating side is added to this plate making it hexagonal (p. 68). In area C, however, column 

 4 originates in the fourth row, with the result that the plate on its ventral border is heptag- 

 onal (partially restored as indicated by dotted lines), and the initial plate of column 3 is pen- 

 tagonal. A similar case is shown in area C of Lovenechinus septies (Plate 45, fig. 1) but it is of 

 rare occurrence, as column 4 almost always originates in the next row after column 3. Column 

 4 originates on the right of the center in areas A, C, and I, but on the left of the center in areas 

 E and G, with some consequent readjustment of plates (compare Archaeocidaris, Plate 9, figs. 

 6-8;" text-fig. 239 bis, p. 264). Above the fourth row no new columns are added, but all four 

 columns extend to the apical disc where the youngest plates on either side are in contact with 

 the oculars. Two oculars are in place, are widely insert, and imperforate. The three gcnitiils 

 are high, wide, and have each three genital pores. All bear secondary tubercles as shown in 

 Plate 30, fig. 4, in which the absent plates are restored, as indicated by dotted lines. 



I am under obligation to Dr. Bather for the photograph of this specimen which is repro- 

 duced on Plate 29, fig. 1. 



*Palaeechinus ellipticus M'Coy. 

 Plate 29, fig. 2; Plate 30, figs. 8-10. 



Palacchinus ellipticus M'Coy, 1844, p. 172, figs. 3a-3d; Desor, 1858, p. 158; (?) Tornquist, 1893, p. 103; 



(pars) Klem, 1904, p. 31; Lambert and Thiery, 1910, p. 119. 

 Echinocrinus ellipticus d'Orbigny, 1849, p. 126, text-fig. 278. 

 Palaeocidaris (Echinocrinus) ellipticus Vogt, 1854, p. 332, text-figs. 212-214. 

 Non Palai'chinus ellipticus Baily, 1865a, p. 217; non 1865c, pp. 65-67, Plate 3, figs. 2a, 2b; non Quenstedt, 



1875, p. 380, Plate 75, fig. 42. 1 

 Palaeechinus ellipticus (pars) Loven, 1874, p. 41. l 

 Non Palaeechinus ellipticus Duncan, 1889, p. 200, text-fig, viii; (see p. 308, and this memoir, pp. 326, 329, 



where Duncan's specimen is referred to Lovenechinus lacazei). 

 Non Palechinus ellipticus Torncaiist, 1897, p. 739; non Maccoya ellipticus Lambert and ThieVy, 1910, 



p. 119 (both of these names are based on Duncan's 1889, p. 200, text-fig, viii, Pnlncfi-hinux ellipticus, 



here referred to Lovenechinus lacazei as above stated). 



The test is high and elliptical, 51 mm. high, 41 mm. in diameter, width of the ambulacrum 

 at the mid-zone 4 mm., width of the interambulacrum 22.5 mm. About seven and one-half 

 ambulacral plates equal the height of an adambulacral. The observations were made on 

 M'Coy's type specimen in Dublin, which I studied through the kindness of Dr. Scharff, who 

 also kindly supplied me with a cast and the photograph here reproduced. 



The ambulacra are narrow, composed in each area of two columns of low plates, all of which 



1 These several references to Palaeechinus ellipticus as a synonym are in regard to a specimen that Baily described as 

 that species but is here referred to P. quadriserialis (pp. 305, 306). 



