LEPIDECHINUS. 397 



*Lepidechinus iowensis sp. nov. 

 Plate 62, fig. 1 ; Plate 63, figs. 3, 4. 



Test spheroidal. Known only from the holotyiae, which measures 52 mm. in diameter. 

 The ambulacra at the mid-zone are 4.5 mm. in width and the interambulacra 28 mm. in width. 

 The ambulacra are narrow, composed of two columns of low primary ambulacral plates alike 

 throughout the area. Pore-pairs are uniserial, situated near the outer border of each plate. 

 Ambulacral plates imbricate slightly adorally and laterally bevel under the adradials (Plate 

 63, fig. 4). The interambulacra are broad with five columns of plates in each area. The in- 

 terambulacral plates are moderately curved outward, are pentagonal in adambulacral and 

 hexagonal in median columns. They imbricate moderately aborally and from the center 

 outward and over the ambulacrals, on the adradial suture line presenting a curved outline 

 (compare Perischodomus, Plate 64, fig. 3). The ventral portion and apical disc are wanting, 

 but the lantern is in place and partially visible, as seen from above (Plate 63, fig. 3). The 

 lantern is inclined, so that, with the angle presented, one sees a considerable portion of the inner 

 face of the teeth (compare Plate 27, fig. 5). The teeth are grooved, pyramids wide-angled, 

 and foramen magnum moderately deep. Typical braces are in place. The structure of the 

 lantern as far as gathered from the dorsal view is essentially like that of Lepidesthes (Plate 68, 

 figs. 9-14). 



Upper Burlington Limestone, Lower Carboniferous, Burlington, Iowa. The holotype 

 and only known specimen is in Mr. Frank Springer's collection 8,010. 



*Lepidechinus tessellatus sp. nov. 

 Plate 62, figs. 2-4; Plate 63, figs. 5-11. 

 Lepidcchinus imbricafus A. Agassiz, 1904, p. 80 (non Lepidechinus {mbricaius Hall, 1S61, p. IS. See p. 299). 



Test spheroidal. The holotype (Plate 62, fig. 2) measures 50 mm. in diameter. The width 

 of the ambulacrum at the mid-zone is 5 mm., width of the interambulacrum 25 mm. 



The ambulacra are narrow, composed of two columns of low primary plates in each area. 

 Pore-pairs are uniserial, situated near the outer end of each plate (Plate 63, fig. 6). About 

 five to six and a half ambulacral plates equal the height of an adambulacral. The ambulacral 

 plates imbricate adorally and laterally bevel under the adambulacrals. From this beveling 

 it occurs that the ambulacral plates on the interior of the test (Plate 63, fig. 7) are wider than 

 on the exterior, and also on the interior the pore-pairs are in the middle of the half-areas instead 

 of near the outer end of each plate, as on the exterior (p. 60). 



The interambulacra are wide, composed of six columns of plates at the mid-zone in each 

 area. In the paratype (Plate 63, fig. 9) the sixth column originates below the raid-zone, and 



