420 ROBERT TRACY JACKSON ON ECHINI. 



Palaeechinus ekgans, but a further examination of his specimen convinced me that his observa- 

 tion was a mistake, and that the plates are imperforate, as earlier discussed (pp. 309, 363). 

 An accidental pit due to weathering can easily be confused with a structural pore; but there 

 seems no reason for believing that these supposed ocular pores are other than what they 

 appear. The oculars adorally cover the ambulacra and laterally the interambulacra quite 

 widely on either side. The genitals are wide, and almost square in shape, riot produced 

 ventrally in an elongate apex as usual in the Palaeechinidae. There are two or three pores to 

 a genital plate, and one of the plates has clearly marked fine madreporic pores, this being one 

 of the few cases in which this structure has been seen in Palaeozoic species (p. 172). On 

 account of the presence of the madreporite, the figures (Plate 66, figs. 4, 5; Plate 68, figs. 4, 

 5) are oriented correctly by the Lov^n method, which usually cannot be applied because the 

 true axes are not known. The periproct is covered with many small plates, which are more 

 rounded in outline than in the Palaeechinidae, but are similar to the same plates in Lepidesthes 

 colletti (text-fig. 251, p. 428). 



The lantern is quite fully known, more so than in any other species of the genus (Plate 68, 

 figs. 9-14). The lantern is inclined as usual in the Palaeozoic. The pyramids are wide-angled, 

 with a moderately deep foramen magnum; the lateral wings of the pyramids have plicate 

 ridges for the attachment of interpyramidal muscles. The teeth are grooved (Plate 68, fig. 9). 

 The epiphyses are narrow, capping the half-pyramids, and laterally have a glenoid cavity and 

 tubercles for interlocking with the brace as in modern regular Echini. The brace is a block- 

 shaped plate with condyles that fit into the glenoid cavities of the epiphyses (Plate 68, figs. 12- 

 14), as in all regular Echini, living and fossil (p. 181). 



Kaskaskia Group, Lower Carboniferous, Pulaski County, Kentucky, holotype and para- 

 type, University of Chicago Collection 6,604; F. Springer Collection 8,042 and other speci- 

 mens; Sloan's Valley, Pulaski County, Kentucky, F. Springer Collection 8,023, 8,027, 8,033, 

 8,043, and other specimens; United States National Museum Collection 42,349; Chester Group, 

 Lower Carboniferous, Huntsville, Alabama, United States National Museum Collection 

 37,716. 



*Lepidesthes devonicans Whidborne. 



Plate 68, figs. 15-17. 



Lepidesthes (?) devonicans Whidborne, 1896, p. 376; 1898, p. 200, Plate 24, figs. 1,2; Plate 25, figs. 3a-3f. 

 Lepidesthes devonicans Lambert and Thiery, 1910, p. 123. 



Test very large, form unknown. Whidborne estimated that it was three inches or more 

 in diameter. The specimens in the Museum of Practical Geology consist of two slabs which 

 are counterparts and bear the impressions of plates. One of the specimens, no. 7,160, is a mold 

 of the interior, and the other, no. 7,161, is a mold of the exterior, and bears impressions of tub- 



