390 



DR F. A. BATHEE. 



121. Stem, measurements in millimetres : — 



1 



Total Length 

 Preserved. 



Length 



of Proximal 



Region. 



Circa 



Width at 



Proximal 



End. 



Width at Distal 

 End. 



E 16021 

 E 16018 



E 16020 



75 



94 



81 complete 



15 



9 

 13 



9-5 



lo" 



10-2 



17 



•8 



•7 and then 

 tapers rapidly to 

 a point 



Of these specimens, only El 6021 preserves the complete theca, and of this the 

 height is ca. 27 mm. Since the stem here is incomplete its length was at least three 

 times that amount, and that is likely to have been the usual proportion in the species. 



§ 122. Distal region. In El 6020 the extreme tip is seen— a rapidly tapering point 

 like the end of a cigar (PI. I. fig. 8). There is no sign of any form of attachment here 

 or in any other specimen ; and there is scarcely room for doubt that this is the com- 

 plete distal end. Two fragments, which also appear to be distal ends, are preserved in 

 E16013 (PL I. fig. 9). 



The combined dimeres form almost a cylinder, slightly tending to a barrel shape, 

 with a length of about 4 mm. where the diameter is 2 mm. (El 60 18) or between 

 1*8 mm. and 27 mm. (El 6021). The lumen has a diameter of 7 mm., and is very 

 slightly constricted towards the middle of each cylinder (E16018). 



§ 123. In the Median region the dimeres at first alternate, and then are pushed 

 apart by intercalated plates often of lozenge shape. These latter increase in size, while 

 the dimeres gradually become shorter, so that in the proximal part of this region the 

 stem is composed of polygons approximately equal in size but irregular in shape 

 (PI. I. figs. 6, 7). 



§ 124. This merges into the Proximal region, well shown in the actual stereom of 

 El 6021 (PI. I. fig. 7). Here the ossicles are roughly divisible into two sizes. The 

 larger ones are transversely elongate and are gathered into circlets, interspersed with a 

 few smaller ossicles to fill up gaps between the larger ones. The spaces between 

 successive circlets are filled by smaller ossicles, and are depressed. The general effect 

 is that of a stem composed of columnals alternating in size, or of the flanged columnals 

 common in Cystids. The more prominent among the larger ossicles are arranged in 

 vertical series, continuing the larger ossicles of the middle region, or intercalated as the 

 present region widens towards the theca. The number of these main vertical series at 

 the proximal end cannot have been less than five or more than eight. In some cases 

 {e.g. El 60 18) this moderate amount of regularity persists right up to the theca; in 

 other cases {e.g. El 6021) the ossicles for a distance of some 3 mm. immediately below 

 the theca are quite irregular, and it is not easy to draw a definite line between columnal 

 and thecal elements. 



