220 PLATE LXXV. 



Habitat. — Shetland ; 170 fathoms ; J. G. Jeflfreys, 

 Esq. and the Rev. A. M. Norman. 



Examined. — In the dried state. 



This sponge was dredged at Shetland in 1867 by 

 Messrs. J. Gwyn Jeffreys and the Rev. A. M. Norman. 

 It is fanshaped, with a sessile base of about four 

 inches in length. The width of the whole sponge 

 slightly above the base is ten and a half inches, and 

 its greatest height seven and a half inches. The 

 average thickness does not exceed half an inch. The 

 primary fan is nearly in the same plane, but somewhat 

 irregularly sinous, and from about the middle of its 

 concave surface there is a secondary fan given oif at 

 nearly right angles to the primary one. In the dried 

 condition the sponge is remarkably fragile. 



The surface is nearly even but not smooth, and the 

 whole substance of the sponge is perforated so as to 

 present the ai^pearance of rough irregular lacework ; 

 the hispidation is not visible even by the aid of a two 

 inch lens, but in sections of the sponge at right angles 

 to its surface it is seen to be a well produced and con- 

 stant character. It is caused by the radiation of the 

 terminal spicula of the primary lines of the skeleton 

 fibres of the sponge. Neither oscula nor pores are 

 apparent. 



The dermal membrane is pellucid and thin; it is 

 rather abundantly fmmished with its various spicula. 

 The tension spicula are frequently as long as the 

 skeleton ones, but not more than one fourth or one 

 fifth of their diameter. The attenuato-acuate internal 

 defensive spicula are small and slender, and appear 

 more especially to belong to the membranous struc- 

 tures, upon which they are lying amidst the numerous 

 retentive ones. Both forms of retentive spicula are 

 very minute, rarely exceeding in length the diameter 

 of a skeleton spiculum; they are about equally 

 numerous, aud very nearly of the same size. One 

 of the anchorate form measured YbTS inch in length, 

 and an average-sized bihamate one — 4V0 ™ch in length ; 



