72 PROCEEDINGS OF THE ACADEMY OF [1889. 



the Cliona celata, which he observes is the most destructive species 

 to oyster shells, and abounds in the Frith of Forth. His paper is 

 accompanied by a figure of the sponge occupying an oyster shell, 

 and the author remarks that the Cliona undoubtedly works out the 

 cavities it inhabits, whether mechanically or otherwise. He attributes 

 the boring power to silicious granules on the surface of the sponge 

 and to its contractility. The silicious granules are figured as 

 hexagonal plates with hexagonal markings. Mr. Hancock also 

 describes boring-sponges found in a number of other molluscous 

 shells, which sponges he referred to several other different species of 

 Cliona (Annals and Magazine of Natural History, Vol. VIII, p. 

 321). 



N. Lieberkuhn, in 1859, described the Cliona celata as living in 

 oyster shells at Heligoland, and attributed the boring of the shells 

 to the sponge (Archiv fur Anatomie, Vol. 26, 515). 



Dr. Bowerbank, in his work on the British Spongidae, II, 1866, 

 212, referred the Cliona celata of Dr. Grant, to another genus, with 

 the name of Hymeniacidon celata., to which he also refers the other 

 boring-sponges described by Mr. Hancock. He reports it as occur- 

 ring in all parts of Great Britain in oyster and other shells, and 

 also in limestone rocks of Tenby. Dr. Bowerbank doubted the 

 boring power of the sponge and regarded it as merely occupying the 

 deserted habitations of living annelids. Rev. A. M. Norman, editor 

 of the fourth volume of the same work, remarks that Dr. Bower- 

 bank persistently refused to entertain any other opinion than that 

 the Cliona only occupied previously-formed excavations, and had 

 no power of penetrating shell or stone. 



Dr. Johnston is the only European authority who ascribes a mas- 

 sive form of sponge to the same species as the ordinary boring form 

 of oyster shells. Dr. Bowerbank describes and figures a large mas- 

 sive sponge, common on the British coast, under the name of Rap- 

 hyrus Griffithsii, and refers to it the massive variety of Halichondria 

 celata of Dr. Johnston, observing that it is not a matter of surprise 

 that it should have been confounded with Dr. Grant's Cliona 

 celata, the spicula of the species being so very similar in size and 

 form. 



Dr. 0. Schmidt describes Cliona celata,\mder the name of Vioa 

 celata, occurring on oysters and stones in the Adriatic, and remarks 

 that its spicules are pin-like and of one kind only, (Supplement der- 

 Spongien des Adriatischen Meeres, 1864, 40). His distinctive char 



