430 



MR. F. A. EATHEE OX PETALOCRi:S'rS. [Aug. 1898, 



The thickness at the distal end of the arm-fans can rarely be 

 observed ; in b it is 1 mm. ; in d, arm i about 1 mm. ; and in 1 it is 

 1*2 mm. The angle that the facet makes with the ventral surface 

 of the fan can be estimated only in b, where it is 83° ; in e, where 

 it is 75° ; and in 1, where it is 78^. 



The first primibrach, seen only in this species, has a height along 

 the dorsal line of '5 mm. in specimens a and d, and has the same 

 width as the facet of the radials and the arm-fans. Towards the 

 ventral surface its height decreases. 



The ridges between the grooves sometimes widen considerably 

 at the distal end, as in b, but there is no sign of branching beyond 

 16 finials. The ridges are generally rounded, narrower than the 

 grooves, and, when favourably preserved, display notches for 

 covering-plates alternating on either side (as in specimen b). The 

 covering-plates are not preserved, but one seems to see their 

 impressions in specimen f 1, arm ii, as previously described on 

 pp. 415, 416 (PI. XXYI, fig. 47). 



Meastjbeme^^ts op Doesal Cups (in millimetees). 



Heio^ht 



Width from R to IR .... 



Basals, height 



,, width 



Radials, height 



„ width 



Column, width 



Width between arms i-ii . 



» ii-iii. 



„ hi-iv. 



„ iv-Y. 



,, ^-i • 

 Greatest width of crown . 



6 

 1-3 



1-7 

 2 



3 

 1 



2-5 

 2-5 

 2 



2-5 

 2 

 26-5 



1-6 

 4-4 

 1 



? 



1-5 

 2-3 

 1 



2? 

 1-7 

 1-5 

 11 

 1-5 

 20-5 



f 1 



? 

 6 



? 

 ? 

 ? 



3-6 



? 



2-2 

 2-5 

 2 



1-6 

 2-5 

 31 



f2 



g 



Q 



9 



3-25 



4 



9 



9 



? 



1-2 



9 



9 



9 



9 



■5 



9 



•75 



1 



1 



1-2 



1 



1 



1 



•0 



1 



1 



13-5 



22 



The dorsal cup, since it is known only in this species, has been 

 described in detail under the head of ' General Anatomy.' In 

 specimen a it is tilted a little on one side, exposing portions of the 

 tegmen (PI. XXVI, fig. 43) ; the sutures are fairly distinct. In c 

 the cup is doubtless present, but covered by matrix. In d 

 (PI. XXVI, fig. 38) the cup is clear, but the sutures less distinct 

 than in a. In f (PI. XXVI, fig. 46) the cup is removed, and only 

 the impression of the tegmen marks its former presence. In f 2 

 (PI. XXVI, fig. 37) the sutures of the small cup cannot be distin- 

 guished : either they were anchylosed in life, or have been obscured 

 by petrification. In g (text-fig. 1, p. 401) some of the cup-plates 

 have been broken away, and only their outer casings left, as 

 explained in the ' Description of Material ' (p. 405). 



The columnals are known only in this species, and, as shown in 

 specimen c (PI. XXVI, figs. 48-50), have already been described 



