318 A MONOGRAPH OF THE 



ston in his ' History of British Sponges,' while others as- 

 sumed a widely expanded form of cup, very shallow in 

 depth, and having a diameter of as much aS eight or ten 

 inches, and a few of the number were fan-shaped. I also 

 received from fifteen to twenty specimens, from the Hebrides 

 and Loch Fine, dredged by Mr. Archibald McNab, a fisher- 

 man of Inverary. These specimens were remarkably 

 small, few of them exceeding an inch and a half in height. 

 I have also had the pleasure of seeing, through the kind- 

 ness of the late lamented Dr. Meming, the specimen 

 described by him in his ' History of British Animals,' and 

 it is undoubtedly the same species as those I have received 

 from Shetland. 



The whole of the specimens mentioned above are from 

 northern locahties, but in 1861 Mrs. Collings, the lady of 

 the Seigneur of Sark, found a small specimen at St. Martin's, 

 Guernsey. It was of the same size as those obtained from 

 Loch Fine, not exceeding an inch in height, having the 

 usual form of a small cup. The hispid character of this 

 sponge is not readily detected in the fresh condition. It is 

 produced by the projection of the terminal spicula of the 

 primary lines of the skeleton. The characteristic structure 

 of the skeleton in the genus Isodictya, is strikingly ex- 

 emplified in this sponge, even to the extent of the primary 

 and secondary lines of structure having separate and dis- 

 tinctly different forms of spicula. Those of the primary 

 lines being almost always attenuato-acuate, and having 

 their apices directed towards the distal portions of the 

 sponge ; while those of the secondary lines are as uni- 

 formly acerate. Occasionally a single spiculum of either 

 form will be found out of place ; but these cases are the 

 exception, while the separation of the two forms is the 

 rule. 



30. Isodictya dissimilis, Boioerbank. 



Sponge. Pedicelled, branching and anastomosing iii nearly 

 the same plane. Surface even, hispid. Oscula simple, 



