18 Trans. Acad. Sci of St. Louis. 



1896. Lepidocentrus rhenanus. Jackson, Bull. Geol. Soc. 

 Amer., vol. 7, p. 224. 



Interambulacral plates nearly hexagonal, with the corners 

 rounded. Five columns in each intrambulacrum, and two in 

 each ambulacrum. 



Geological formation and locality: Devonian, Wipper- 

 fiirth. 



b. Perischodomus M'Coy 1849.* 



1 Syn. Perischocidaris Neumayr 1881. f 



Homotoechus SoUas 1892. t 



Tretechinus Tornquist 1897. § 



Body round or nearly so. Interambulacra broad, consist- 

 ing of five columns of irregular plates. Adambulacral plates 

 larger and bearing one perforated tubercle near the ambu- 

 lacral edge. Other plates covered with small granulated 

 tubercles close together. Ambulacra consist of two columns 

 (sometimes more) of small, low plates pierced by a pair of 

 pores each. Spines smooth and cylindrical. Mouth and 

 anus small, both central. Genital plates pierced bj^ six or 

 eight pores. Plates imbricate. 



1. Perischodomus bisf:rialis M'Coy. 



1849. PeHschodonius biserialis. M'Coy, Ann. Mag. Nat. 

 Hist., ser. 2, vol. 3, p. 253. 



1S54:. Perischodomus biserialis. M'Coy, Cont. Brit. Pal., 

 p. 115. 



1858. PeriscJiodomus biserialis. Desor, Syn., p. 157. 



1862. Perischodomus biserialis. Dujardin et Hupe, Echino- 

 dermes, p. 466. 



1874. Perischodomus biserialis. Loven, Kongl. Svens. Vet- 

 ens. Akad. Handl., bd. 11, no. 7, p. 40. 



* Ann. Mag. Nat, Hist., ser. 2, vol. 3, p, 253. 



t Sitzb. K. Akad. Wiss. Wien, Math. Naturw. CI., b;L 84, ablh. 1, p. 174. 



X Sclent. Proc. Roy. Dub. Soc, n. s. vol, 7, pt. 3, p. 153, 



§ Abhdl. Geol, Karte Elsass-Lothringen, Bd. 5, heft 6, p. 784. 



