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VI. Description of a new Species q/" Euplectella (Euplectella Cucumer, 0.). 

 By Professor Owen, F.B.S., V.F.L.S. 



Read February 17th, 1857. 



In 1841 I communicated to the Zoological Society of London a description of a new 

 generic form of reticulate Alcyonoid Sponge, represented by one of the most singular and 

 beautiful, as well as the rarest, of the marine productions with which the researches of 

 Mr. Hugh Cuming itt the PhUippiae Islands had enabled Mm to enrich his famous 

 Natural-History collection*. For tliis genus the name Ihiplectellai was proposed, indi- 

 cative of the exquisite regularity and complexity of the interweaving of its component 

 threads. 



The characters of the genus are : — a cylindroid hollow form of body, closed at the 

 wider end by an irregular network, and at the narrower end by the terminal tuft of finer 

 filaments into which the pai'ietal fibres are there resolved. 



The parietal fibres, or those that constitute the wall of the cylinder, are regularly dis- 

 posed, and intersect each other at definite and nearly equal distances throughout its 

 extent. They consist of longitudinal (PI. XXI. fig. 1, c, d, e), transverse {t), and oblique 

 fibres, the latter being of two kinds (o, o'), winding spii'aUy round the cylinder, but in 

 opposite dh'ections : (see magnified view of part of the parietes, PI. XXI. fig. 4). The 

 longitudinal and transverse fibres are the thickest : they are arranged at intervals of from 

 one to two lines, averaging one line and a haK aj^art, and divide the cylinder-wall into 

 square spaces (a) of about the latter diameter. The longitudinal fibres (fig. 4, b) are 

 external to the transverse ones (t), to which they axe bound by the oblique or spiral 

 fibres; these are, some external, some internal, to the others, and they close by their 

 decusastion alternate quadrate intervals {k) between the longitudinal and transverse fibres. 

 The angles of the alternate open squares are intersected by finer and less regular oblique 

 fibres, which reduce their area more or less to a circular form (fig. 4, a). 



It appeared, in the first-described species, that the fine silky filaments into which the 

 parietal fibres were resolved at the small end of the cylindroid, had been torn, or detached 

 by violence from some other body. The subject of the present description, which has been 

 liberally confided to me for that purpose by my friend Dr. Arthui" Farre, F.R.S., has 

 been fortunately preserved, along with the foreign body to which it was attached by the 

 terminal filaments : such mode of attachment may now, therefore, be added to the generic 

 characters of Euplectella as above defined. 



The fiLTst-described species of this rare genus was founded on a specimen eight inches 

 in length, of a slightly conical form, two inches across the base, and gradually and pro- 

 gressively decreasing in diameter to the truncated apex, which is one inch and a quarter 

 in longest diameter {. 



* Transactions of the Zoological Society of London, vol. iii. p. 205. t Gr. eJ, well, irXtKw, I weave. 



I Trans. Zool. Soc. vol. iii. pi. 13. 



