48 
TWO BLASTOIDS FROM SOMERSET. 
respect the specimen figured by Etheridge & Carpenter seems to 
agree with it rather than with the holotype. The trigonal section 
of the base is equally indistinct in the only Belgian specimen 
possessed by the British Museum [E. 8239], a slightly crushed 
theca from Tournai. 
millimetres, 
The measurements 
ascertained, are ; — 
far 
they 
be 
Waterlip 
Figg. of 
De Kon. & 
Le Hon. 
Statement 
of De Kon. 
& Le Hon. 
Eth. 
and 
Carp. 
B.M. 
E. 8239. 
14*0 
end j 
3'4 
1 1 -8 
f 14*0 or'l 
t 12-4 i 
3-2 
IO'O 
7'3 
8-5 
2'I 
ca 9*o 
7.2 
7*5 
De Kon. 
Figure of 
Holotype. 
Height of theca 14*2 14*0 15*5 17*0 
Antero- \ g >2 
posterior dia. / 
Transverse "I 
>ca 7*3 
diameter] ' 0 
Diameter at 
proximal en 
The ratio of height to diameter appears so much greater in 
the English specimen that one is almost tempted to regard it as 
at least a new variety. But it would be rash to take any such 
step on so insecure a foundation as the self-contradictory figures 
and statements hitherto published. 
The piece of stem appears from its position to be the proximal 
region of the stem belonging to this theca ; but closer examina- 
tion shows this to be unlikely. It seems to be a single columnal, 
7-4 mm. long, with a diameter of 37 mm., that is to say slightly 
exceeding- the proximal diameter of the theca. Both joint-faces 
are flat, and marked with fine ridges radiating- from a lumen of 
•9 mm. diameter, and undoubtedly larger than the lumen at the 
base of the theca. 
Acentrotremites elli r ptic%is (Cumberland). 
(Plate, figs. 3—7.) 
For references to literature see " List of the genera and species 
of Blastoidea," British Museum, 1899. 
The specimen [Brit. Mus., E. 8256] comes from the Visean 
Dibunophyllum (D 2) zone of the Carboniferous Limestone at 
Wrington, Somerset, and is coloured dark red outside (Figs 3-5). 
The holotype has disappeared and its provenance is uncertain. 
The specimen figured by Etheridge & Carpenter [Brit. Mus., 
E. 782] is labelled " Carboniferous Limestone, Somerset," and is 
coloured like that from Wrington (Figs. 6 and 7). The fact that 
Cumberland described his specimen as consisting " of perfectly 
white limestone, filled with brown calcareous crystals," does not 
necessarily militate against its having come from the same stratum 
as those now before me, for their red colouring, though charac- 
teristic of the Dibunophyllum beds, is superficial, and Cumberland's 
words apply absolutely to specimen E. 782 ; the substance of the 
plates is white calcite. The Wrington specimen confirms the 
view that Somerset is the home of "Mitra elliptica" and first makes 
certain the horizon of the species. 
