REPORT OX THE POLYZOA. 
1.61 
The growth, which is of a most beautiful pearly aspect, completely covers the valve 
of a Terebratula, the zocecia being disposed in parallel linear series, radiating irregularly 
from the centre. 
The only difference of any importance between this form and the typical Lepralia 
( Mucronella ) ventricosa is in its having eight oral spines instead of four. In this respect 
it corresponds with Mr. Hincks’ Lepralia ( Mucronella ) peachii var. /3 octodentata with 
which indeed it is in all probability identical. But that it is a form of Mucronella ventricosa 
and not of Mucronella peachii is obvious from the other characters, amongst which 
perhaps the most important is the great width of the internal denticle. The great 
convexity also of the zooecia and the deep sulci between them, together with the forward 
position of the ooecium and the peculiar radiate sculpturing of the surface of the zocecia 
and their large size, seem to be sufficient to show that the present form should be referred 
to Mucronella ventricosa. One remarkable feature presented by it is the extreme 
diversity in size of the zooecia ; the central ones being perhaps less than half the size 
of those at some distance from the centre of the colony. It also exhibits in a very 
marked degree the great changes undergone at different stages by the peristome, which, 
in Mucronella ventricosa , as Dr. Manzoni remarks, “ e tanto pill largo et calloso, quanto 
piu la cellula e avvanzata in eta.” 
8. Aspidostoma, Hincks. 
Eschara (sp.), Ek. 
Character. — Zoarium dimorphous, uni- or bi-laminar ; erect, solid, rising from a con- 
tracted calcareous base, or expanded and foliaceous. Zooecia with the front depressed 
in the centre and the sides tumid. Mouth quite at the summit of the depressed area, 
concealed under the tumid border, on which above the mouth is a penthouse-like, usually 
bifid projection. The mouth arched above, straight below, and protected in front by a 
broad shield-like plate or mucro which is continued downwards for some distance within 
the zooecium. 
Aspidostoma, giganteum, Busk, sp. (PI. XXXIII. fig. 3). 
Eschara gigantea , Bk., Brit. Mus. Cat., vol. i. p. 91, pi. cxix. fig. 3. 
Aspidostoma crassum, Hincks, Contrib. Ann. and Mag. Nat. Hist., ser. 5, vol. vii. p. 47, pi. x. 
figs. 6, 6a, 1881. 
Character. — Zoarium erect, bi- or uni-laminar. Zooecia broadly pyriform or hexa- 
gonal, very convex or tumid in front, depressed in the centre. Surface granular, 
walls very thick and massive, rounded on the sides ; separated by deep sulci. Mouth 
quite at the summit of the depressed area concealed under the tumid border, crescentic 
(ZOOL. CHALL. EXP. — PART XXX. 1884.) Gg 21 
