452 ROBERT TRACY JACKSON ON ECHINI. 



that there are apparently five columns of interambulacral plates, and the same number is given by 

 Fraipont, based on his more nearly complete specimen. Julien's best figure shows a column of 

 pentagonal adradial plates and in part smaller hexagonal plates of median columns. A large 

 adambulacral plate measures 14 mm. in width and 8 mm. in height. Fraipont's photographic 

 figure shows an ambulacrum which is about the width of one interambulacral plate. He does 

 not describe the structure but as gathered from his figure it probably has two columns of pri- 

 mary plates, or primary and occluded plates at the mid-zone which structure would refer the 

 species to either the genus Palaeechinus or Maccoya. 



Lower Carboniferous, Regny, Neronde, Saint-Germain-Laval, central France; type in the 

 possession of the family of the late Professor Julien. Marbre Noir de Dinant, Belgium (Frai- 

 pont). 



Palaechinus robineti Julien. 

 Palaechinus robineti Julien, 1896, p. 129, Plate 3, fig. 19; Lambert and Thiery, 1910, p. 119. 



Fragmentarily known. According to Julien, there are two columns of low narrow plates 

 in an ambulacral area, each plate with two pores and 2.5 to 3 mm. wide by 1 mm. high. The 

 ambulacrum therefore is about 5 to 6 mm. wide. The character of the ambulacrum fixes this 

 species as belonging to Palaeechinus proper. Five ambulacral plates equal the height of an 

 adambulacral. Of the interambulacrum there are pentagonal adambulacral and hexagonal 

 median plates, but, as these are dissociated, the number of columns in an area is unknown. 

 According to Julien, adambulacral plates are 5 mm. wide and 3 mm. high, the hexagonals 7 mm. 

 wide by 4 mm. high. These measurements must have been taken from plates of different zones 

 in the area, for hexagonal plates are necessarily nearly or quite the same height as adambul- 

 acral plates in the same horizontal row, and also the height given for adambulacral plates 

 does not equal the 5 mm. which is what Julien says is the height of five ambulacrals which 

 equal the height of an adambulacral. As the number of interambulacral columns is unknown, 

 this species cannot be placed systematically in its relation to other species of Palaeechinus, 

 and if known, it might prove to be the same as some already described species. Julien's 

 figure is too indistinct to be recognizable. 



Lower Carboniferous, La Varville, Siguret, central France. Holotype in the possession 

 of the family of the late Professor Julien. 



Palechinus sp. Tornquist. 

 Pdechinus sp. Tornquist, 1897, p. 763, Plate 20, fig. 6; Klem, 1906, p. 37. 



A single small pentagonal adambulacral plate is figured; its genus is doubtful. 

 Lower Carboniferous, Hunsriicken, Germany. 



