250 A MONOGRAPH OF THE 



other, while in mature specimens they are frequently dis- 

 persed in parallel lines in a very regular manner, and in 

 other cases there appears to be no order in their dis- 

 position. The variety of forms of bihamate spicula is 

 greater than I have hitherto found in any single species, and 

 comparatively they are large. 



Of three specimens in my possession, two of them have 

 the oscula scarcely raised above the general level, while the 

 third has a portion of them considerably elevated on large 

 tumid prominences. 



My specimens were taken from the east side of St. 

 Katherine's Rock at Tenby, a little above low-water spring 

 tides. I have one from Mr. M 'Andrew, who dredged it in 

 deep water near Shetland. 



This species is the one described by Dr. Grant in his 

 admirable papers on ' The Structure and Functions of the 

 Sponge,' under the name of S. panicea, in the ' Edinburgh 

 New Phil. Journal,' i, 343, and ii, 138. Dr. Johnston, in 

 his c History of the British Sponges,' has placed Dr. Grant's 

 JS. panicea as a synonym of H. panicea, Johnston ; but as 

 the type of that species is the " sponge-like crum of 

 bread" of Ellis, it is manifest that the synonym is an error. 

 I am indebted to Dr. Grant for one of the original specimens 

 on which he made his observations, and I am therefore 

 enabled to make this correction safely; for although its 

 external characters are not so strikingly developed as in the 

 specimens from Tenby and the Hebrides, its anatomical 

 characters are so peculiar as to leave no doubt on the sub- 

 ject. On examining and comparing the organization of the 

 type specimens of Halichondria incrustans and Hal. saburrata 

 in the Johnstonian collection of British sponges in the 

 British Museum, I found the structural characters to be 

 precisely identical. The author in his specific characters of 

 the latter species, ' History of British Sponges,' p. 120, 

 inadvertently describes the spicula as " short, curved, and 

 double-pointed ;" in page 197 of the same work he corrects 

 this error, and describes them as " short, obtuse at one end 

 and pointed at the other ; and, in fact, so like those of 

 Halichondria incrustans, as perhaps to prove that II 



