124 Mr. T. H. Withers on 



there is an abundant fauna of Brachiopods, Gastropods, 

 Orthoceratites, Ostracods, Crinoids, Cystids, and Polyzoa. 



So far the genus Plumulites has not been recorded from 

 the Kuckers Shale or from Estbonia, although it has a wide 

 geographical distribution and comprises several species 

 ranging through the Ordovician, Silurian, and Devonian 

 rocks. It is but rarely that the plates are found in their 

 natural position, and in consequence most species are known 

 by detached plates only. In many cases the species have 

 been described either under Turrilepas or Flumulitts (see 

 Withers, 1915, p. 122) in the belief that those two genera 

 are synonymous, as indeed they are regarded even in recent 

 text-books. 



Mr. Bekker has collected and has recently submitted to 

 me thirteen pieces of the bituminous Kuckers Shale on which 

 are exhibited a number of plates which undoubtedly belong 

 to the genus Plumulites, s. str., but cannot be referred with 

 our present knowledge to any of the known species. 



Genus Plumulites, Barrande. 



The shell of this genus was probably blade-shaped and 

 composed of four vertical columns of plates, although in 

 most cases where the shell is at all complete the four 

 columns are flattened and spread out ; the plates themselves 

 are extremely thin. The two admedian columns of plates 

 are heart-shaped, and, although flattened out in the fossils, 

 were in life probably bent at an angle along the median fold 

 observable in all these plates ; and, although they appear 

 merely to abut along the margin of their inner lobe, they 

 probably overlapped to some extent, but they do not alter- 

 nate with, or intersect, each other; the outer lobe of each 

 plate intersects the outer plates on either side. The outer 

 kite-shaped plates, as do the admedian plates, overlap each 

 other from behind forward ; they are slightly curved distal- 

 wards and have a strong narrow median fold, and usually a 

 much narrower submarginal fold on either side ; these two 

 latter folds probably mark the position of the plates above 

 and below. Plates in which the apical part is broadly 

 rounded and the growth-lines form a series of rings at the 

 apex (" cancellated " plates of Barrande) have been found 

 associated with the other plates, and these cancellated plates 

 were probably modified plates forming the basal or proximal 

 extremity of the shell. 



