XI. Balanoecrinus. 403 
about 10 mm., the. middle one (Order III) in each case 
being very slightly higher than the two others (Order LV). 
The difference in diameter can scarcely be measured, and 
probably does not amount to more than ‘05 mm. on the 
outer angles, but it is more apparent on the re-entrant 
sides, 
Forbes said that the section was more stellate in younger 
specimens. There is, however, no correlation at all between 
size and stellation or lobation, but the correlation with 
alternation that does exist indicates that the proximal region 
is more stellate or lobate. 
This leads us to consider the two specimens hitherto 
separated as Pentacrinus sowerbit (E 5888, 4,6). They 
were fairly well represented in Sowerby’s engravings (fig. 4); 
ais the fragment in matrix, 6 the isolated fragment. They 
belong, however, to a single stem, which has broken at the 
syzygy so that the epizygal with 2 facets is on J and the 
hypozygal ona. The cirrals attached to the epizygal are 
shown at the top end of Sowerby’s figure. Diameter 
5°4: mm. ; section quinquelobate. In dare 25 internodals, 
which appear to be in three orders, though possibly it should 
be four. The height of the epizygal (Order I) is 1:3; that 
of Order II about 1:0; of Order III ‘*9 to°8; of Order IV 
‘6 to'5 mm. The arrangement, starting at the proximal 
eres. Uligy BV, AL ty pait, Ivy, BES te: Ivy DE, 8v;; 1a, HT, 
11, 1v, II, 111, 1v, I, rv, m1, Il, 1v, m1, I. The differences 
between the orders are more marked in their diameters, 
and may amount to ‘5 mm., but the condition of the 
specimen renders exact measurement difficult. 
Owing to the confluence of the crenellae in most cases, 
the suture-line is rarely crenelate. The following speci- 
mens, however, show some crenelation at the interradial 
angles: 57542 a, d,e, E 21967, E 21969. All these are 
somewhat lobate or stellate. Crenelation might be detected 
in other examples were it not for their patination. Its 
presence, of course, indicates that the crenellae have not yet 
become confluent so as to form an entire margin—for 
instance, the association of a crenelate suture-line with 
confluent crenellae, as in Forbes’s fig. 10, is merely evidence 
of imaccuracy. Crenelation is therefore rather a sign of 
youth, or, in conjunction with lobation, of recent formation, 
as in the proximal region. As one would expect therefore, 
crenelation is best seen in P. sowerbii, where it is almost 
obscured on fragment 5, but very clear on fragment a. In 
the latter the crenelation extends over the sutural margin 
down the side-face towards the equator of the columnals, 
y i es 
