158 
THE VOYAGE OF H.M.S. CHALLENGER. 
in the larger ones the mandible is acute, sword-shaped, pointing directly upwards ; in the 
smaller, rounded. Ocecium globose, very prominent, finely punctured all over, and 
sometimes, having at the lower part, in front, a rounded papillary eminence, supporting 
a minute avicularium. Dorsal wall entire. Zooecia about 0 //, 02 wide. Orifice 0"*01 wide. 
Habitat. — Off Bahia, 10 to 20 fathoms. Station 122, lat. 9° 5'S., long. 34° 50' W., 
32 to 400 fathoms, red mud. 
It is of a deep bright brown colour. The description is taken from specimens that have 
been boiled in caustic soda. In the natural state the surface is covered with a uniform 
chitinous epitheca, to which the colour is mainly due, and which conceals the sculpture 
of the surface. It occurs in the collection only in broken fragments which show no sign 
of its having been attached to anything. The posterior surface is smooth and divided 
into convex, oblong, imperforate spaces, corresponding to the outlines of the zooecia. 
In some respects closely resembling Escharella lamellosa, Smitt ; the differences 
between that arctic form and the present are amply sufficient to distinguish them. 
Amongst these may be noted (1) that in Escharella lamellosa the wall of the zooecium 
is entire and imperforate except a row of elongated punctures round the border, whilst 
in Mucronella castanea the surface is closely punctate all over ; (2) in Escharella 
lamellosa there are normally 3 to 5 oral spines above, and the surface of the 
ocecium is smooth, and presents three round pores in front, and usually an ovate stigma 
on each side below, whilst in Mucronella castanea the surface of the ocecium is very 
finely and beautifully punctate all over, and is furnished with a small circular papilliform 
avicularium on each side below. 
What the general habit of the zoarium may be cannot be determined from the frag- 
mentary specimens in the collection. 
(8) Mucronella magnifica, n. sp. (PI. XVIII. fig. 3). 
Character. — Zoarium expanded, suberect. Zooecia subovate, or rhomboidal, or irregu- 
larly hexagonal behind ; convex in front and behind ; covered with a very thin dark 
brown epitheca. Anterior wall very thick, closely punctate ; posterior thin, transversely 
wrinkled with from 1 to 4 or more rounded perforations, from which, in the upper part, 
radical tubes issue ; four lateral interzooecial plates. Orifice orbicular with a broad 
central mucro on the lower border and two lateral acute points (not internal denticles) ; 
four articulated marginal spines above. A conical, rostral projection in front, immediately 
below the orifice, supporting on one side of its summit an avicularium, with a broad 
duck-bill shaped mandible. On one or both sides of the orifice but not close to it is 
a large avicularium, with an elongated, duck-bill shaped mandible, pointing obliquely 
upwards. Ooecium large, lofty, and very prominent, the front prolonged downwards 
