464 Mr. H. J. Carter on the 



ments of a new species which I am about to describe under the 

 name oiArabesculajMi'cisitica, together with exquisite skeletons 

 of many Polycystin» and circular frustules of Diatomaceae, &c. 

 In short, I should think that a careful examination of this 

 mass of detritus, after the manner mentioned, would, if 

 furnishing an amount of deciduous remains proportional 

 in number and variety to that which came from the minute 

 fragments of the Farrea that I boiled in nitric acid, yield 

 sufficient not only to copiously illustrate a book with most 

 exquisite figures, but to afibrd no mean catalogue of the 

 sj)onge-fauna, Polycystinaj, and marine DiatomaccEe of that 

 part of the Seychelles from which this specimen of Eujdectella 

 cucumer was obtained. 



Lastly, I have to desciibe the structure of a new genus of 

 sponges, apparently allied to the Lithistidfe, which Avas first 

 observed on some fragments of the deciduous skeletons of 

 Ajjhrocallistes Bocagei and Farrea occa respectively, from the 

 specimen No. 3 a dredged up by H.M.S. ' Porcupine,' and 

 subsequently seen among the minute spicules &c. just men- 

 tioned which were boiled off the fragments of the two 

 Farreoi from the root-mass of Euplectella cucumer. The 

 resemblance of this structure, which lies flat and parasitic on 

 the deciduous glassy fibre mentioned, to that kind of sculptured 

 "open work" used by the Mohammedans for their architec- 

 tural windows before glass was made for this purpose, suggests 

 the generic name of ^^Arahescula " — and the manner in which 

 it has grown over the deciduous fibre mentioned, the specific 

 ^^ parasitica-^ " under which appellation it will now, so far as 

 the bare skeleton permits, be described : — 



Arabescula, nov. gen., Carter. 

 Arabescula parasitica^ n. sp., Carter. (PI. XVII. figs. 7-9.) 



Skeleton corticiform, vitreous, thin, spreading, composed of 

 frond-like spicules, each of which is formed of a sinuous, ver- 

 micular body, tortuously branclied in all directions on the 

 same plane (fig. 8, a) ; branches ending in filigreed termina- 

 tions, which, interlocking with those of adjoining fronds, con- 

 stitute a membrane-like expansion (fig. 7, b). Body smooth 

 externally, provided with sparsely scattered, short, truncated 

 cylindrical projections (fig. 8, h) on the inner side, Avhich, 

 being situated on the body and larger branches, rested on the 

 vitreous fibre over which the sponge might be growing. 



Hab. Marine, growing over deciduous fibre of Aphrocallistes 

 Bocagei and Farrea occa. 



