LOVENECHINUS. 335 



columns of interambulacral plates is Maccoya intermedia, and so far this species has been re- 

 corded from Ireland only. The two larger specimens which Fraipont doubtfully refers to 

 lacazei have each four columns of interambulacral plates, and are quite similar in appearance 

 to the Kirkby Stephen specimen (Plate 35, fig. 7), so that I should equally refer them to Loven- 

 echinus lacazei. 



Lovenechinus mutatus (KVyrs). 



Plate 38, figs. 10, 11. 



Oligoporus mutatus Kcyes, 1894, p. 12(i, Plate 15, figs. 4a, 4b; 1895, p. 183, Plate 18, figs. 4a, 4b; Klem, 

 1904, p. 39; Lambert and ThieYy, 1910, p. 121. 



Test spheroidal, with strongly marked melon-like ribs. Ambulacra less than half the 

 width of the interambulacra, composed of four columns of low plates at the mid-zone, two of 

 narrow demi-, and two of wide occluded plates. Pore-pairs in peripodia lying in that portion 

 of each plate nearest the marginal portion. Occluded plates elevated in a high, steep, median, 

 rounded ridge. According to Keyes's figure, the occluded plates do not enter between the 

 demi-plates in a tongue-like fashion, as in L. nobilis (Plate 38, fig. 6), but the contact is rather 

 serrate, as in L. septies (Plate 45, fig. 3) and Oligoporus danae (Plate 50, fig. 7). According 

 to his figures also each demi-plate bears one small secondary tubercle and each occluded plate 

 bears three or four of the same in a nearly continuous horizontal row. 



The interambulacra are wide, steeply rising from the adradial suture, then roundly curved 

 across the area. There are five columns of plates in an area at the mid-zone, the adradial plates 

 are pentagonal, the median hexagonal, their surfaces covered with small secondary tubercles. 



This species is known only from Dr. Keyes's original description ; the holotype is in the 

 private collection of Mr. L. S. Cox of Keokuk, Iowa. It is smaller than, but structurally close 

 to L. nobilis, from which it differs in the single row of tubercles on ambulacral plates, the shape 

 of demi- and occluded plates at their point of contact and the carinate edges on the sides of 

 the interambulacra where they dip down to the adradial sutures. 



Keokuk Limestone, Lower Carboniferous, Keokuk, Iowa (Keyes). 



*Lovenechinus nobilis (Meek and Worthen). 

 Plate 37, figs. 1-3; Plate 38, figs. 4-9. 



Oligoporus nobilis Meek and Worthen, 1868, p. 358; 1873, p. 476, Plate 11, fig. 3; Loven, 1874, p. 42; 



Keyes, 1895, p. 182; Jackson, 1896, p. 198, Plate 6, fig. 35; Klem, 1904, p. 39; Lambert and ThieVy, 



1910, p. 121. 

 Melonopsis nobilis Meek and Worthen, 1873, p. 478. 



This fine species is spheroidal in form with elevated melon-like ribs. The plates are the 

 most massive of any known Echini. Measurements of the type as given by Meek and Worthen 



