PAZ^OZOIC FOSSILS. 295 



GENUS LEPIDECHINUS (Hall). 



Lepidechinus : Hall, Descript, New Species of Crinoidea ; Preliminary Notice, 



p. 18. 1861. 



This genus was described as " Subspheroidal, the form and arrangement 

 '* of the ambulacral and interambulacral series as in Paleciiinus, with 

 " the plates of the interambulacral series imbricating from the dorsal side, 

 " and the lower edges of each range overlapping those below; while the 

 " plates of the ambulacral areas are imbricating in the opposite direction, 

 *' narrow and deeply interlocking at their joining edges, each plate pierced 

 " near the opposite extremity by two pores. Surface granulose." 



This genus was separated from Palechinus on account of the imbrica- 

 ting character of the plates, both of the ambulacral and interambulacral 

 areas, and also from the more numerous ranges of plates in the interam- 

 bulacral areas. In its essential characters, it is much further removed from 

 that genus.* 



Lepidechinus has a double range of poral or ambulacral plates, and 

 two pores in each plate near the outer end, making two double rows of pores 

 only ; while the interambulacral areas are many times as wide as the ambu- 

 lacral areas, and differ from those of Palechinus in having more than 

 five ranges of plates. 



Lepidechinus rarispinus (n. s.). 



PLATE IX. FIG. 10. 



Body spherical or depressed spheroidal. Interambulacral area having from 

 nine to eleven ranges of imbricating, mostly hexagonal plates, in their 

 widest part, which gradually decrease in size towards the upper end ; 

 while on the lower side the central ranges terminate, and the outer ranges 



. only reach the oral aperture. The plates are imbricated from below up- 

 wards, and from the centres of the areas outwards ; the central range 

 overlapping those adjoining on either side. The ranges immediately bor- 

 dering the ambulacra are small, and mostly furnished with small spines. 

 The plates of the next range are the largest of the body ; each alternate 

 plate in the upper part larger than the adjacent one, and having a strong 



*Dr. B. F. Shumard, in his Catalogue of Palaeozoic Fossils, in adopting the generic 



name Lepidechinus, adds : " Compare Oligoporus (Meek & Wortrkn)." I am at 



a loss to understand any near analogy with a fossil having the '^ambulacral areas 



" about half as wide as the interambulacral spaces," and the " ambulacral pores iu 



" four ranges with some irregular intercalated smaller pieces between," and having 



'* the pores in pairs, two to each piece, and arranged in four double rows, two on 



** each side of the mesial ridge or convexity of each ambulacrum. 



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