356 Rev. T. Hincks on the Genus Retepora. 
margin produced into a tall mucronate process, broad below 
and narrowing towards the apex, bent outwards, and bearing 
on its summit a minute avicularium, with rounded mandible ; 
peristome elevated on one side of the mucro into a broad, 
wing-like process, produced at its upper and outer angle into 
a pointed spine; a slit-like fissure between the mucro and 
the lateral process, closed above, but forming a looped foramen 
below; elongate, linguiform avicularia, with a very delicate 
mandible, distributed over the zoarium, frequently one on the 
front of the cell towards the side. Dorsal surface vibicate, 
with many small subcircular and linguiform avicularia, irre- 
gularly placed. Ooecia elliptical, smooth, with a narrow 
longitudinal fissure. 
Height (of the largest specimen examined) a little more 
than 4 inch, breadth about ? inch. 
Hab, On stones &c., deep water. : 
Localities. Off the Land’s End (2. @. Couch) ; south-west 
of Polperro, on stone, 40 fathoms (7. 17.) ; Guernsey (Rev. A. 
M. Norman). 
Distribution. Mediterranean, 390 fathoms (‘ Porcupine’ 
expedition, teste Busk). 
fiange in time. Italian Pliocene beds (Manzon‘). 
The very much produced and recurved rostrum, with its 
minute terminal avicularium and the wing-like elevation of 
the peristome on one side of it, are the most salient and 
striking features of this species. But it is also distinguished 
from its allies 2. Beaniana and RK. cellulosa by differences in 
the avicularia and fenestre, From the former it is also sepa- 
rated by the presence of an oral fissure. 
This is probably the form which Borlase records from 
Scilly, and which Couch includes in his ‘Cornish Fauna’ under 
the name of AR. reticulata, though it is quite impossible to 
identify it by their descriptions. I infer that it is the 
same species, because no other south-western Retepore has 
been brought to light by recent dredgings. 
2. letepora pretenuis,n. sp. (Pl. XIX. figs. 6-8.) 
Zoarium forming a simple, reticulated frond, more or less 
curved and contorted. Fenestre usually of large size, elongate, 
and narrowed towards both extremities; the branches very 
slender, commonly composed of only two rows of cells. 
Zooecia ovate, very slightly convex, smooth; orifice sub- 
orbicular, peristome not elevated, a small fissure on the lower 
margin, and beside it usually a minute avicularium with 
rounded mandible; on the front of the cell, a little below the 
mouth, frequently a raised elongate avicularium ; mandible 
