418 



3iS. F. A.. BATHEE OX PEIALOCErXITS. f-^Ug. 189S, 



of the curve that the brachials were arranged in regularly concentric 

 rings, just as they are in Crotalocrimis, and in the proximal series 

 of Eaallocrinus punctatus and Gissocrinu^s camjpanula (^see ' Crinoidea 

 of Gotland, 1/ pi. ix, fig. 294). 



The axial canals are thus proved to branch with the ventral 

 grooves, and bo extend with them at least as far as the III Br. 

 That they continue to run along to the distal ends of the grooves, 

 even of adult specimens, has been proved by study of P. vishi/censis. 

 Pirst, transverse sections made by grinding (specimen n, PI. XXV, 

 fig. 11 & text-fig. 6), or natural cleavage-fractures across the arm- 

 fan in more distal regions (specimens j & p, PL XXV, fig. 10), enable 

 one to see the axial ca^ials, usually as dark spots, underneath the 

 grooves. Secondly, some specimens (such as h and i, PI. XXV, 

 fig. S), when seen from above, show holes through the floor of the 

 ventral grooves into the underlying axial canals. Thirdly, iu grind- 

 ing the horizontal section (specimen w, text-fig. 7), one could, in 



Fig. 6. — Petalocrinus visbycen- 

 sis. Series of sections across the 

 proximal end of specimen n. 



I is the most prosdmal, IV the most 

 distal. 



v.g., ventral groove ; a.c, axial canal ; 

 s, trace of original suture between 

 arm-branches; St., secondary stereom. 



The actual appearance of a stage in 

 crrindiug slightly more distal than IV 

 is shown in PL XXV, fig. 11. The 

 course of the grooves is shown in text- 

 fig. 8, n (p. 423). Magnified about 

 iC diam. 



Pig 



— Petalocrinus visbycen- 

 sis. Horizontal section of arm- 

 fan, specimen w. 



^ 



J 



The lighter parts represent the trans- 

 lucent stereom; the broad, branch- 

 ing, darker parts (?'.^)are the ventral 

 grooves, or grooves 4- axial canals, 

 filled with matrix ; the light mark- 

 ings {h) in the middle of some of 

 these latter represent portions of 

 the stereom bridging over the axial 

 canals ; the dark markings (s) are 

 the pigmented traces of the stroma 

 originally filling the sutures l5e- 

 tween the arm-branches. The misty 

 appearance of the middle of the 

 drawing shows that, owing to the 

 curvatm-e of the fan, the above- 

 mentioned structures here give place 

 to the dorsal stereom. Lrawn by 

 Mr. G. Venman. [x 4 diam.] 



