116 
THE VOYAGE OF H.M.S. CHALLENGER. 
Habitat. — Station 161, entrance to Port Phillip, 33 fathoms, sand. Station 162, off 
East Moncceur Island, Bass Strait, 38 fathoms, sand, shells. 
This is a very remarkable form, from its size and peculiar mode of growth. The 
description of the zooecia is taken from some at the growing edge, for in the older portions 
of the zoarium the characters are completely obscured by their crowded growth and deep 
immersion. The oral spines, though apparently not articulated, are very slender and 
fragile, and consequently are often wanting. The anterior avicularia are very small and 
inconspicuous, and may easily be overlooked. A great characteristic is the fine 
irregularly hexagonal areolation of the dorsal surface, and the existence of the minute 
umbonal avicularian papilla in nearly all the areolse. The peculiar formation of the ocecia 
is also remarkable. 
(9) Retepora atlantica, n. sp. (?) (PI. XXVIII. fig. l). 
(?) Rete'pora cellulosa, var. marsupiata, Smitt, Florid. Bryoz., pi. xiii. figs. 245-254. 
Character. — Zoarium an inch or more in diameter, infundibuliform or irregularly 
cupped, flexuose, white and pearly. Fenestrse oval, pretty uniform, not quite as wide as 
the trabeculae. Zooecia (young) subeylindrical, free above ; surface smooth. Orifice sub- 
orbicular. Peristome slightly thickened, often a slender spine on each side towards the 
front, and sometimes, especially in the lateral zooecia, rising on one side into three or four 
obtuse teeth. Labial fissure terminating in a round suboral pore ; one angle thickened 
and prominent, supporting a small avicularium with a semicircular mandible. Ooecia 
deeply immersed, with a very short vertical fissure with con- 
verging sulci or rugae. Anterior avicularia adventitious on the 
front of a zooecium, varying much in size and sloping almost 
perpendicularly downwards. Mandible membranous, sword- 
shaped and apiculate. Dorsal surface smooth, vibicate, with 
elongated areolae, and beset with numerous avicularia, seated 
chiefly on the sides of the fenestras, with an elongated ensiform 
apiculate membranous mandible. 
Habitat. — Station 75, lat. 38° 38' N., long. 28° 28' 30" W., 
450 fathoms, volcanic mud. 
[(?) Gulf of Florida, Smitt ; Tenerife, W. K. P. ; Adriatic, 
Heller.] 
This form so closely corresponds in many respects with 
Professor Smitt’s species, that I am strongly inclined to think 
they may be the same. The operculum varies somewhat in size and form, and perhaps 
could scarcely be distinguished from that of Retepora beaniana or Retepora cellulosa , 
