Crinoidea, Pentacrininae. 33 
all other respects, the description of the specimens provides a welcome supplement 
to the description of the typical Isocrinus tyrolensis. As holotype of the subspecies 
is taken the original of Pl. Il, fig. 44. 
Description of the Specimens. — Transverse section varies from a 
slightly excavate rounded pentagon (fig. 46) to a decided pentapetalon with almost 
semicircular lobes and sharper but rounded reéntrant angles (fig. 38). Excavation 
greatest at the epizygal. The stem-fragments being curved as a rule, the following 
measurements in millimetres are based on averages : 
Diameter of internodals 22 28 31 34 39 40 40 -41 438 43 44 
Height » » Oo Cea 09 0s 09 02.094 07 O77 08 O07 
Ratio, height: diameter 24 S50 34 425 43 44 425 585 558 537 6:28 
Height of epizygal. . 09 09 10 09 1109 10 O8 10 095 08 
The first of these, being young, has a ratio—diameter: height:: 100:43. This 
differs so greatly from the others that it is not included in the diagnosis. It agrees, 
however, with the rule that relative height decreases with age. Really, the second 
specimen, with its low internodals, is more aberrant, but probably comes from the 
proximal end of the stem and contains many ‘freshly formed columnals. 
Internodes short; out of 15 specimens, 10 have 5 internodals, and 5 have 6. 
Only in one case are there as many as 6 columnars following on the epizygal 
without clear signs of a hypozygal. The frequency of nodes is further proved by 
the large number of nodals in the collection; out of the whole 34 specimens, only 
2 insignificant fragments show neither epizygal nor hypozygal. The fragments nearly 
always end at a syzygy, and in 15 out of the 34 they consist of a complete 
intersyzygium. 
There is slight variation in the height of adjacent columnars. The nodals 
(order I) are about 071 mm. higher than the adjacent internodals. In an internode 
of 5 (fig. 44), the orders of size are arranged thus, beginning with the epizygal of 
the intersyzygium above: I, III, IV, II, IV, Ill, I. If there be 6 internodals (fig. 45), 
the added columnar appears to be the hypozygal, since the formula is now I, IV, 
Ill, 1V, Il, IV, Ill, 1. These differences, though not always very apparent, are more 
pronounced than in the Tyrolese specimens, and are enough to confirm the view 
that those specimens cannot be merely younger forms. The differences of diameter 
and relative height between J. tyrolensis and J. tyrolensis major are therefore 
due, not to difference of age, but to absolute differences in size and mode of 
growth. The conditions of life in the Balaton district were perhaps more favourable 
to the growth of the species than were those at St. Cassian, and permitted the 
crinoid to grow larger more rapidly or to continue its growth to a greater age. The 
former alternative is supported by the small number of internodals, and is consistent 
with the observations of A. D. Meap*, who has shown that in Asterias Forbesi 
the rate of growth and the age of sexual maturity are entirely dependent on the 
food-supply. 
Side-faces straight, with suture-lines scarcely depressed. In a few, and chiefly 
in the more excavate, there is a slight convexity, whereas in a few there is a slight 
* Amer. Natural. XXXIV, p. 17; Jan., 1900. 
Resultate der wissenschaft!. Erforschung des Balatonsees. |. Bd. 1. T, Pal. Anh. 3 
