424 ROBERT TRACY JACKSON ON ECHINI. 



and 3,174 (from R. T. J. Coll.); Yale University Museum Collection 317; Freiburg i. B., 

 Germany, Museum, one specimen. 



The holotype in the Michigan Museum has the original label in Meek's handwriting. It is 

 imperfect dorsally but otherwise well preserved, and is well represented in Professor Meek's 

 figure here reproduced as Plate 66, fig. 10. There are ten columns of plates in ambulacral 

 area B, and in interambulacrum A the introduction of the sixth column is seen just below the 

 mid-zone. On the reverse side the tips of a strong lantern are in place. There is also a second 

 specimen of this species in the University of Michigan Collection 150, which I studied through 

 the kindness of Dr. A. G. Ruthven. The second specimen is much larger than the type, 

 measuring 60 mm. in height. In one ambulacral area it has twelve columns of plates and six 

 columns in two interambulacral areas. 



Mr. Braun's (Plate 66, fig. 8) is the finest specimen of the species seen. It has ten columns 

 of plates in an ambulacral area and six columns of plates in two interambulacral areas. At 

 the zone represented by the figure (Plate 68, fig. 18) only five interambulacral columns were 

 visible. This specimen has numerous secondary tubercles on ambulacral and interambulacral 

 plates and spines about 1 mm. in length. 



In the University Museum at Freiburg in Breisgau, there is an excellent specimen of this 

 species, which I studied through the kindness of Professor Georg Boehm. It is large, about 

 60 mm. high, and there are ten columns of ambulacral plates in an area. Ventrally, in one 

 interambulacrum the primordial interambulacral plate is in the basicoronal row, and additional 

 columns come in as above described; also parts of a lantern occur as above described. 



*Lepidesthes carinata sp. nov. 

 Plate 66, fig. 11. 



This species is known from one specimen only, which is worn, so that details are not very 

 clear. The test is large, with strongly elevated ambulacral areas recalling the melon-like ribs 

 of Melonechinus, but here the whole area is involved instead of mainly the two median columns 

 of occluded plates as in that genus (Plate 60, fig. 3). This species and Perischocidaris harteiana 

 (p. 408; Plate 65, fig. 1) are the only members of the Lepidesthidae in which melon-like ribs 

 have been observed. The diameter of the test is about 65 mm.; the ambulacrum is about 25 

 mm. wide, and interambulacrum about 11 mm. in width. 



There are twelve columns of plates in an ambulacral area and six columns of plates in an 

 interambulacral area at the mid-zone. This species is structurally similar to Lepidesthes coreyi, 

 but differs in the strongly elevated ambulacral areas. 



Keokuk Group, Lower Carboniferous, Crawfordsville, Indiana; holotype in Museum of 

 Comparative Zoology Collection 3,175. 



