1889.] ON NEW OR RARE SPECIES OF PLEXAURIDS. 47 
4. Descriptions of some new or rare Species of Plexaurids. 
By F. Jerrrey Bevt, M.A., Sec. R.M.S. 
[Received January 28, 1889. | 
(Plate III.) 
Among the Gorgonids in the British Museum there are examples 
of some species of the genera Plewaura and Plexaurella which 
appear to be still undescribed. As to a number of the described 
species, it is often impossible to say with certainty whether or no 
one has them before the eyes; Milne-Edwards and Haime, like 
Duchassaing and Michelotti, make no use of the characters of 
the spicules, though the works of both were published after the 
appearance of Valenciennes’s suggestive essay". Fortunately the 
British Museum is in possession of a series of preparations by 
M. Potteau which may be regarded as illustrative of Valenciennes’s 
memoir, and by the aid of these it is often possible to add enough to the 
otherwise imperfect diagnoses of the earlier describers of these forms. 
Of the species now to be described it may be said that they have 
all such well-marked characters that it is unlikely that any previous 
description of them can have been overlooked.. One of them will 
always rank with the most splendid members of a group which, as 
all know, contains so many remarkable and beautiful forms ; another 
was long since recognized to be a distinct species by the late Dr. Gray. 
1. PLEXAURA PRINCIPALIS. (Plate III. fig. 1.) 
An exceedingly fine form; the whole colony a large bushy mass of 
a uniformly light-brownish colour. Allied to P. suffruticosa, but 
rather less ramose, the terminal branches longer, the branches not 
so flexuous and very rarely nodose; calyces not so closely packed. 
The specimen under description is 86 cm. high, 1°38 m. in spread ; 
the base is flattened from side to side, and its long axis is at right 
angles to the chief plane of spreading ; the greatest length of the axis 
is about 90 cm. The primary trunks are flattened, vary in size and 
are only seldom swollen; the terminal branches are rounded, and 
are often, though not always, about 10 cm. long. ‘The orifices of 
the calices are rather small; they are generally about 1 mm. apart, 
but sometimes they are separated by 2 mm., and occasionally they 
are a little more distant from one another. Cortex smooth, mode- 
rately thick; axis black, not very flexible. 
The characters of the cortical spicules may be best made out from 
the accompanying figures’; for the purpose of comparison the 
spicules of P. suffruticosa are, now for the first time, figured; the 
chief points to be noted are that P. imperialis appears to have no 
spicules of the so-called ‘ Blattkeule”’ form ; the four-rayed spicule 
is rare, and is either vestigial or rudimentary in character. The 
elongate spicules are longer and more delicate than in P. suffruticosa ; 
1 Comptes Rendus, xli. p. 7 et seg. 
2 All the spicules figured in the accompanying drawings (Plate III.) are 
magnified about 180 times. 
