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THE VOYAGE OF H.M.S. CHALLENGER. 
with a bluntly mucronate lower border ; afterwards the peristome rises in front into a 
rather slender median mucro, usually with a shorter one on each side or sometimes two. 
Three or four non- articulated oral spines above. A projecting 
avicularium on one or both sides of the front low down, with 
an acutely pointed mandible pointing upwards and outwards ; 
surface granular. Ooecium rounded, subimmersed. Surface 
granular. 
Habitat. — Station 315, lat. 51° 40' S., long. 57° 50' W., 
12 fathoms, sand and gravel (on Fucus). Simon’s Bay, Cape of 
Good Hope. Prince Edward Island, 80 to 150 fathoms. 
[Tierra del Fuego and Chiloe Archipelago, Darwin ; Curtis 
Island, Bass Strait, Hincks.] 
On the Fuegian specimens the avicularia are sometimes 
much larger, but the mandibles present the same forked basal end. 
The characters of Mucronella tricuspis are seen with great difficulty except at the 
growing border. The accompanying woodcut represents the chitinous organs, which are 
quite sufficient for its identification. 
Fig. 45 . — Mucrcmella tricuspis. 
(11) Mucronella simplicissima, n. sp. ? (PI. XXII. fig. 5). 
Character. — Zocecia very distinct, fusiform, subtubular, and curved forwards above ; 
surface smooth, entire, porcellanous. Orifice orbicular, with a small pointed mucro in 
front ; peristome very slightly thickened. 
Habitat. — Station 161, off Port Philip, 33 fathoms ; sand (on dead shells). 
Probably merely an adnate variety of Mucronella pyriformis. 
(12) Mucronella ventricosa, var. multispinata, Busk (PL XXII. fig. 11). 
Lepralia multispinata, Bk., Quart. Journ. Micr. Sci., N. S., vol. i. p. 77, pi. xxxii. figs. 5, 6, 1861. 
1 Mucronella peuckii, var. /3 octodentata, Hincks, Brit. Mar. Polyz., p. 361, pi. li. fig. 2. 
Character. — Zocecia ventricose, immersed below, convex in front and much raised, 
almost tubular above ; surface granular, with a row of minute distant pores near the 
border. Orifice subclithridiate, mucronate in the young state ; peristome in mature 
zooeeia thick, much raised and projecting in front, with six to eight erect, long, and strong 
spines on the sides and behind ; but usually broken off. A broad denticle some distance 
within the orifice. Ooecia prominent, small, globular ; surface granular. 
Habitat. — Station 148, lat. 46° 47' S., long. 51° 37' E., 210 fathoms, hard ground, 
{jravel and shells. Prince Edward Island, 80 to 150 fathoms. 
O 
