354 ROBERT TRACY JACKSON ON ECHINI. 



surface ornamentation is not preserved, but it doubtless bore small secondary tubercles as in 

 related species. The ventral portion and apical disc could not be ascertained in the type. 



A specimen in the Museum of Comparative Zoology Collection 3,008, which I described 

 previously (1896) and referred to this species, is an internal view. Ventrally, the ambulacral 

 plates are not very well preserved, but are seen to cross the half-area. Higher up the plates 

 are in four columns, demi- and occluded, and the pore-pairs are in the middle of the half-areas, 

 as seen on the interior of Lovenechinus. In the interambulacrum there are two plates in the 

 basicoronal row, three plates in the second row, and four in the third. The fifth column comes 

 in in the sixth row, and as seen in another area, the sixth column comes in three rows above the 

 fifth, apparently in the ninth row. This specimen is preserved as calcite plates in a clay matrix, 

 stained yellow with iron. The locality given on the label is Indiana, and Mr. Springer informs 

 me that material of this character occurs at Crawfordsville, so that the specimen probably 

 came from that locality or its vicinity. 



This species is very close to blairi and sulcatus; the difference from blairi is its more strongly 

 elevated melon-like ribs, and the difference from sulcatus is the sharply angular character of 

 the interambulacral areas of that species where they dip down to the adradial sutures. These 

 differences are slight, but they are sufficient, it seems, to maintain these as distinct species, 

 although in the number of columns of interambulacral plates they are practically identical. 



The specimen which I identify as the holotype is in the University of Michigan Collection 

 147, from the Keokuk beds of Crawfordsville, Indiana. It bears the locality and identification 

 in Meek's handwriting, and corresponds with the original description in essential features, 

 so that it is undoubtedly the type; another specimen from Crawsfordsville is in the British 

 Museum Collection E 4,273. A third specimen, in the Museum of Comparative Zoology 

 Collection 3,008, as described above, and probably from the same locality, is the only other 

 known specimen of the species. 



"Oligoporus sulcatus Miller and Gurley. 

 Plate 47, fig. 10; Plate 48, figs. 3, 4. 



Oligoporus sulcatus Miller and Gurley, 1893, p. 8, Plate 1, figs. 4, 5; Lambert and Thiery, 1910, p. 121. 

 Melonites multiporus (pars) Klem, 1904, p. 43. 



The specimen is silicified, test high, spheroidal, with strongly marked and quite angular 

 melon-like ribs in ambulacral and interambulacral areas. The holotype, which is the only 

 known specimen, measures 53 mm. in height, and 65 mm. in diameter through the mid-zone, 

 in the plane J, E. Ambulacra measure 13.5 mm. in width, interambulacra 25 mm. in width 

 at the mid-zone. The surface detail is corroded and gone in parts, especially ventrally, as 

 seen in the photographic figures, but the essential specific features can be ascertained. The 

 ambulacra at the mid-zone (Plate 47, fig. 10) consist of four columns of narrower demi- and 



