XI. Balanocrinus. 387 
brought from Biarritz by Mr. S. P. Pratt, on which the 
Austins founded their P. prattii, and it is these which form 
the basis of the present study. They are registered E 21943- 
FE 22028. 
The first question to settle is the generic position of the 
species. In 1888, when arranging the Tertiary crinoids in 
the Geological Department of the British Museum, I labelled 
the specimens of this and some other species as Balanocrinus, 
a genus which previously had not been recognized later than 
the Cretaceous period. It does not, however, appear that 
this ascription has ever been published in so many words, 
and down to quite recent years geologists continued to refer 
to the Biarritz fossil as Pentacrinus didactylus. Of course, 
it is not a Pentacrinus sensu stricto ; what these writers 
mean is [socrinus (see ‘ Pentacrinus : a Name &e.,’? Natural 
Science, xii. p. 245, April 1898). 
Characters of Balanocrinus.—This section was separated 
from Isocrinus by de Loriol, first as a subgenus (1879, 
‘Monogr. Crin. foss. Suisse’), subsequently, with the 
approval of P, H. Carpenter, as a full genus (1889, ¢ Paléont. 
Frang., Jurassique, Crinoides,’ part 2, p. 295). The dia- 
gnostic characters were drawn solely from the stem, no other 
portion being then known with certainty. ‘Translated into 
modern terminology (see Bather, 1909, ‘Trias. Echin. 
Bakony,’ pp. 24-30) and revised, they are as follows :— 
Transverse section varies usually from circular to penta- 
gonal, and rarely to somewhat quinquelobate. Side-faces 
usually smooth, but may be granulate. A radial depression 
and pore sometimes present. Normal joint-face with peri- 
pheral crenellae short, tending to form a continuous series 
of subequal crenellae round the margin; with adradial 
crenellx opposite and set at right angles to the perradius, 
but always reduced in size, often to mere granules, and thus 
forming single or double rows passing along the perradius 
from the central area to the crenelate periphery. Thus the 
petal-floors are separated from each other by straight 
boundaries. Syzygial joint-face frequently with peripheral 
erenellae reduced in size and adradial crenellae similarly 
reduced or replaced by a single linear groove along each 
perradius, with floors smooth and on the epizygal often 
raised. Cirrus-facets transversely elliptical, as in Jso- 
crinus. 
A fine series of figures was given by de Loriol (1887-88, 
‘ Paléont. frang.,’ tom. cit, pls. clxxxil,—cxcvii,). 
Genotype.— Pentacrinites subteres Miinster, in Goldfuss, 
26* 
