BRITISH SPONGIADJS. 135 



The interstitial membranes are abundant, apparently strong, 

 and are often sinuous in their course. They are furnished 

 with the same description of fusiformi-acerate tension spicula 

 as those of the dermal membrane, but very much more 

 sparingly, and a few of the skeleton or defensive spicula are 

 occasionally embedded amongst them. The retentive spi- 

 cula are very abundantly dispersed over the surfaces of the 

 interstitial membrane as well as on the inner one of the 

 dermal membrane ; they are minute, and very uniform in 

 size. The sarcode is abundant on the interstitial mem- 

 branes, and completely obscures the retentive spicula until 

 a thin section of the sponge is mounted in Canada balsam. 



The general aspect of this species, both in the living and 

 dried states, so closely resembles that of Hymemacedon 

 caruncula that I fully believed it to be that species until I 

 had examined it microscopically. 



I subsequently received a specimen of this sponge from 

 the Rev. A. M. Norman. It was collected at Bantry Bay, and 

 coated a group of shells of a vermetus, nearly two inches in 

 length by one in breadth. The surface of the sponge is 

 very much more rugged and uneven than that from Corn- 

 wall, arising probably from immaturity and the peculiarities 

 of its locality. In all its anatomical details it agreed 

 perfectly with the Cornish specimen. Mr. Norman's 

 specimens were found " on a rock situated about the 

 middle of the entrance of Glengarriffe Hay, extreme low 

 water mark." 



In January, 18G5, I received a specimen, at Hastings, 

 from the Diamond Ground, oval in form, three and a half 

 inches long, one and a half inches wide, half an inch thick ; 

 when alive it was of a full red flesh colour, and the surface 

 with very slight inequalities, but when dried it was exceed- 

 ingly rugged and mammillated by the projection of the 

 terminations of the columns of the skeleton. 



This species may be readily mistaken for M. fallax, at 

 the first view, but when mounted in Canada balsam, and 

 examined with a power of about 400 linear, the abundance 

 of its retentive spicula, and the differences existing in the 

 structure of its skeleton and tension spicula, render the 



