STRUCTURE OF LEFIDOCENTRUS MULLERI. 



223 



centrus mulleri, Schultze, from the Middle Devonian of Muhlenberg near 

 Gerolstein, Eifel. This specimen is in the Ludwig Schultze collection 

 and is the original type of Schultze's species, being figured in his work on 

 Eifel fossils (38), (plate 13, figure 1). 



Theambulacral areas oi Lepido centrus mulleri (figure 2) consist of 2 col- 

 umns of narrow, low, quite regular plates, each perforated by 2 pores. The 

 clearest ambulacrum of the specimen is that seen at the right of the 

 figure. The ambulacrum B^ which should exist between the 2 interam- 

 bulacra figured, A and (7, has been shoved out of view, except in the 

 ventral portion, by the lateral movement of the interambulacra. 



Two interambulacra are quite well preserved, as shown in the figure, 

 and on the other side of the specimen the impress of the plates of two 



Figure 2. — Lepidocentrus miXlleri, Schultze. (Life size). 



other areas can be more or less made out. All interambulacra consist 

 of a large number of columns of plates at what I take to be the dorsal 

 portion, and all are reduced to few columns at the ventral portion, as in 

 Lepidechinus Siiid other genera. 



At the ventral border of area C, as far as preserved (figure 2), 6 columns 

 of plates exist, as indicated by the numbers and dotted lines ; passing 

 dorsally, new columns are rapidly added, as in Lepidechinus (plate 7, 

 figure 42), columns 7, 8 and 9 originating almost simultaneously. The 

 tenth and eleventh columns do not originate until much later than the 

 ninth, and the eleventh originates much too far to the right, according to 

 the ordinary laws of growth, it having at its point of origin eight columns 

 on the left and but two on the right. This highly irregular position may 



