2 THE VOYAGE OF H.M.S. CHALLENGER. 
on 
very irregular, and varying from 8 mm. to 25 mm. in thickness. The branches and 
branchlets are terminated by an apical calicle, The calicles are irregularly placed, 
uniformly circular, varying from 3 to 5 mm. in width, but the average size is 4 mm. 
They are somewhat shallow, slightly prominent at the apical parts, but with a distinctly 
raised margin, becoming very sunken on the thick branches of the base, so as to render 
the general surface very uneven, owing to the prominent intermediate ridges thus 
formed, These ridges are marked by a central depressed line which forms the outer 
limit of the coste, which are very unequal, distinct, and curved. There are usually 
twenty-four septa, but they vary from twenty to twenty-six in a few calicles, slightly 
exsert, and granulated; pali twelve, very granulated, thin, and becoming confluent in 
their inner parts with the well-developed columella. 
This very interesting species, of which one specimen has hitherto been found. 
resembles Oculina banksi (Oculina mammallarts) in many of its characters, but is quite 
distinct from it. 
Locality.— Bermuda. 
Genus 2. Acrohelia, Milne-Edwards and Haime. 
Acrohelia, Milne-Edwards and Haime, Cor., ii. p. 115. ” 
- Duncan, Rey. Madrep., p. 40. 
A single species of this genus is represented. 
Acrohelia horrescens (Dana). 
Oculina horrescens, Dana, Zoophytes, p. 392, pl. xxviii. fig. 1. 
Acrohelia horrescens, Milne-Edwards and Haine, Cor., 11. p. 116. 
Two specimens of this species were obtained. They form many branched clumps 
about 12 cm. high, and but small portions were living when taken. A_ noticeable 
feature of the corallum is its somewhat vesicular structure, beg much less dense than 
in other Oculinidze, and this is apparent even on its outer surface, where it is especially 
marked in the angles of the branches and at the upper junctions of the calicles on the 
basal parts of the corallum. 
Locality.—Banda, taken from the shore at low water. 
Genus 3. Amphihelia, Milne-Edwards and Haime. 
Amphihelia, Milne-Edwards and Haime, Cor., ii. p. 118. 
3 Dunean, Rey. Madrep., p. 39. 
A single species of this genus is represented. 
