242 PLATE LXX\aiI. 



elevated, nearly all on one face of the sponge. Pores 

 inconspicuous. Dermis strongly reticulated, rete irre- 

 gular, polyspiculous ; spicula acerate, short, and stout ; 

 dermal membrane aspiculous. Skeleton very regular ; 

 radial Hues polyspiculous ; secondary lines rarely more 

 than trispiculous ; spicula acerate, short, and stout, 

 same size as those of the dermis. 



Colour. — In the dried state light fawn-yellow. 



Habitat. — Southport, Lancashii'e ? Gr. Graves, Esq. 



Examined. — In the dried state. 



I received three specimens of this species, among 

 other British sponges, from the collection of my late 

 friend Mr. Thomas Ingall, and accompanying them 

 there was a card on which was written, " Southport, 

 Lancashire, G. Graves, Esq." The three specimens 

 varied in size, but in every other external character 

 they resembled each other very closely. The largest 

 specimen was eight and a half inches in height ; the 

 other two were each about five inches high. There is 

 a considerable amount of resemblance between this 

 species and Isodictya siinulans ; they are alike hard and 

 rigid when dried, and the position and general aspect 

 of their oscula are the same. Their sjjicula are also 

 as nearly as possible of the same size and form, but 

 there does not appear to be any disposition on the part 

 of I. Ingalli to assume the latticed form that prevails in 

 J. simulans in its fully-developed condition, and the 

 branches in the latter are stouter than in the former 

 species ; the colour also appears to differ in the two 

 species, but this character is so uncertain that very 

 little reliance can be placed on it. Their external 

 characters will, therefore, scarcely separate the two 

 species, but fortunately their structural pecuHarities 

 readily and strikingly distinguish them. Each of the 

 species has a well-developed, dermal, reticulated 

 system. In I. simulans the rete is unispiculate, and 

 the areas mostly affect a triangular form, but this 

 arrangement does not prevail in the dermis of I. 

 Ingalli, and the rete so abounds in spicula that their 



