Vol. 54.] 



MR. F. A. BATHER OJS- PETALOCROTUS. 



423 



Fig. 8. — Petalocrinus visbycensis. Tracings of arm-fans^ 

 partly restored. (^Nat, size.) 



a 



Notes on the specimens of which measurements are tabulated on p. 4^2. 



a. I^lie four admedian finials are only just beginning, 



b. The distal edge is curiously lobed, not by fracture, and the median ridge is 



not in the line of greatest length. 

 C. There may have been more than eighteen finials. The thickness about the 

 middle of the arm-fan is 1'3 mm. 



d. The distal margin is irregular, perhaps imperfect. This may account for 



the uneven number of branches. 



e. A perfect specimen ; the Type. 



f. A perfect specimen. 



h. Restored in the drawing. The number of brachials may well have baen 18. 



i. Much weathered, both at the ends and sides, 



j is broken at the distal end, so that measurements of length cannot be given. 

 Twenty branches can be seen ; there may have been more. The thick- 

 ness about the middle of the arm-fan is 21 mm. 



k is weathered and rounded, and the facet quite lost. 



1 has lost its facet and a bit of its right-hand distal corner (left-hand as seen in 

 the drawing). 



m is broken at the distal end, and the proximal end appears to constitute an 

 abnormal facet. 



S has lost the distal right-hand quarter. 



V has lost the distal left-hand quarter. 



X lies on the matrix, so that only the ventral surface is exposed ; it is slightly 

 worn all over, especially towards the margins. 



So complete a description of the arm-fan of P. visbycensis has 

 been given under the head of general anatomy that repetition is 

 needless. 



Relations to other Species. — The only species with which 

 the present one is likely to be confased are P. mirahilis and P. infe- 

 rior. Were it not for the shagreen ornament and growth-lines, not 

 always clearly seen even in P. visbycensis, and perhaps only absent 



