418 ROBERT TRACY JACKSON ON ECHINI. 



*Lepidesthes laevis Trautschold. 

 Plate 67, figs. 15-18; Plate 68, figs. 1, 2. 

 Lepidesthes laevis Trautschold, 1879, p. 8, two text-figs. 



This species is known only f ragmentarily ; the form of the complete test is unknown. 

 The ambulacra are wide, but the total number of ambulacral columns is unknown. There 

 must have been, however, at least eight columns of plates, because in a fragment of an ambula- 

 crum in the Berlin Museum (Plate 68, fig. 1) there are six columns as shown, and the right side 

 of this is composed of hexagonal and therefore not marginal plates. To attain a marginal 

 column and also an equal number of columns in each half-area, it is necessary to add two col- 

 umns to those existent, which would give at least eight columns for the area. Ambulacral plates 

 are thin, imbricate strongly adorally, and bevel under the adradials. They bear small secondary 

 tubercles, and the pore-pairs are situated in the upper half of each plate (Plate 67, fig. 15; Plate 

 68, figs. 1, 2). On the interior of the test, the pore-pairs are in the lower half of each plate 

 (Plate 67, fig. 16). This same character of pore-pairs in the lower half of the plates internally 

 is seen in Lepidesthes extremis (p. 431; Plate 7, fig. 2). 



In the interambulacra there are four columns of plates in an area, as shown by Trautschold, 

 but his figures are inverted. The plates are thin, rounded on the suture lines, and imbricate 

 aborally, also from the center laterally and over the ambulacra (Plate 67, figs. 15, 17, 18). On 

 the interior the interambulacral plates are hexagonal in outline instead of rounded, as seen 

 by comparing the outer and inner sides of the same plates in the Berlin specimen (Plate 67, 

 figs. 15, 16). This relation of the interior and exterior of plates in this genus is also shown in 

 text-figs. 32 to 38, p. 75. 



Lower Carboniferous, Miatschkowa, Province of Moscow, Russia; this is the locality 

 given by Trautschold for the cotypes. Moscow, Russia, two specimens in the Museum fur 

 Naturkunde, Berlin, which I studied through the kindness of Professor Jaekel. 



'"Lepidesthes formosa Miller. 

 Plate 66, figs. 4-7; Plate 68, figs. 3-14. 



Lepidesthes formosus Miller, 1879, p. 41, Plate 8, fig. 4; Jackson, 1896, p. 210; Klem, 1904, p. 25; Lambert 

 and Thiery, 1910, p. 123. 



Of this species I have had the opportunity to study a large series of specimens, including 

 the types which were kindly loaned me from the Chicago University Museum by Professor 

 Weller; also some twenty specimens in Mr. Frank Springer's collection, and two in the United 

 States National Museum. This material not only illustrates the species, but also makes addi- 

 tions to the known generic characters. 



