288 A MONOGRAPH OP THE 



rarely more than unispiculous. Spicula sub-fusi- 

 formi acerate, long and slender. Interstitial mem- 

 branes obsolete. 



Colour. — In the dried state, light gray. 

 Habitat. — ^Dundee, Mr. Gardener. 

 Examined. — In the dried state. 



Dr. Johnston, in his ' History of British Sponges/ page 

 112, in treating of Halichandria fucorum renders Mon- 

 tagu's, Gray's, and Grant's species, Sponffia parasitica; 

 Fleming's, Thompson's, and Bellamy's Halichondria para- 

 sitica; and Blainville's Halispongia parasitica, as sy- 

 nonyms of his Halichondria fucorum, and Hal. parasitica 

 holds its place in his index as a synonym only. On 

 examining the Johnstonian collection of British sponges in 

 the British Museum, I found five specimens labelled 

 Halichondria paralitica, which are marked as follows : 

 47.9.7 - 142.22^ — 47.9.7 - 141 - 22». 47.9.7 — 140.22^ 

 47.9.7— 137.22^ and 51.7.25—225. 



The latter specimen is parasitical on a Sertularian 

 Zoophyte about 6 inches in height, from Dundee, by Mr. 

 Gardener, in the forms of five oval lobular masses, each 

 rather less than an inch in height, with a few very much 

 smaller pieces apparently of the same species. On ex- 

 amining two small sprigs of this specimen, each partially 

 enveloped by sponge, I found they were two distinct 

 species, neither of which belonged to the sponge described 

 by him as Halichondria fucorum, which there is little doubt 

 is the one described by Montagu in Wernerian Memoirs, 

 ii, 1 14, as Sponffia parasitica, and neither of the two 

 specimens belonged to the genus Halichondria, as consti- 

 tuted in the present work, but both to the genus Isodictya, 

 to the second division of which also belongs Johnston's 

 Halichondria fucorum. One of the two small specimens 

 also belonged to the second or acuate division of Isodictya, 

 but is a distinct species from /. fucorum, and is described 

 in this work as Isodictya Clarkei. The other specimen 

 belongs to the first or acerate division of the genus, 



