JOURNAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY 



AUGUST, 1879. 



TEANSACTIONS OF THE SOCIETY. 



XXVI. — On a Neiv Species of Excavating! Sponge {Alectona 

 Milla7-i) ; and on a New Species of Rhaphidotheca (B. affinis). 



By H. J. Carter, F.E.S., &c. 



{Bead 11th June, 1879.) 

 Plates XVII. and XVIIa, Figs. 1-4. 



At the request of Dr. Millar I undertake the description of these 

 sponges respectively, prefacing the former with his own observa- 

 tions, which are as follows : — 



" In the month of May last, while looking for sponges on a 

 piece of Amphihelia oculata given to me by Dr. Duncan, I noticed 

 on it numerous small, cribrate, flattish papillae, of a pale ])inkish 

 colour, slightly raised above the surface, which, when detached and 

 examined microscopically, were found to be almost entirely com- 

 posed of spicules so hke those of a Gorgonia that, until tried with 

 acid, I could not be convinced of their siliceous composition. Seek- 

 ing for the form of the largest ones in the late Dr. Bowerbank's 

 ' Monograph of the British Spongiadae,' I found them to correspond 

 with the spicule figured in No. 245,* which Dr. Bowerbank 

 believed ' to belong to a sponge not yet identified.' 



" Having in vain attempted to extricate one of these papillas 



EXPLANATION OF PLATE XVII. 



Fig. 1. — Alectona Millari, n. sp. Longitudinal section of branch of coral of 

 Amphihelia ocu'ata. Dune, showing: — act, excavated portion occupied by Hio 

 Sponge; 6, cribriform papilla; cc, minute processes. 



Fig. 2. — The same. Cribriform papilla, more magnified. 

 „ 3. — „ Skeleton-spicules. 



„ 4. — „ Subskeleton-spicules. 



„ 5. — „ Varieties of subskeleton-spicules. 



„ 6. — „ Flesh-spicules. 



„ 7. — „ Larger variety of flesh-spicules. 



VOL. II. 



Vol. i. pi. xi. 



2i, 



