Spongia coriacca of Montagu. 25 



consisting of two unequal portions divided by a slightly in- 

 flated node which belongs to the longest part, and is therefore 

 a little excentric (fig. 6, c) ; divisions smooth, but more or 

 less varying in thickness here and there, especially towards 

 the ends, which are obtusely pointed ; one division straight 

 and the other a little curved so as to form a very slight angle 

 with the straight one ; largest average size about 91-6000ths 

 inch long by 2-6000ths inch broad (fig. 5, a). 3. Linear- 

 vermiculate, smooth, attenuated towards the extremities, which 

 are pointed ; divided like the foregoing by an excentric node 

 (fig. 5jCc) ; amount of vermiculation and total lengtli very 

 variable, the smallest perhaps about IG-GOOOths inch long by 

 l-6000th inch broad, but immeasurable generally, from the 

 amount of contortion (fig. 5,bb) • increasing in size and de- 

 creasing in vermiculation so as at last to reach an interme- 

 diate form (fig. 5, c/). The triradiates are equally present in 

 the body and stem ; but the linear and vermiculate spicules 

 are exclusively confined to the latter, wliere they form the 

 outer layer and the triradiates the axial or internal structure ; 

 they do not begin to appear before the stem begins to divide 

 into the branches leading to the head (fig. 2, J), and then go 

 on increasing in number and robustness, although not in 

 length, down to the root-like expansion or oldest jjart, as is 

 usual in most sponges. Size of largest specimen (fig. 1) 

 9-12ths inch in total length, of which the body is o^-12ths, 

 and the stem the rest, viz. 5^-12ths inch ; greatest diameter of 

 ■ the body about 3-12ths inch, that of the stem close to the 

 body l-12th, and that towards its base l-24th inch. 



Hah. Marine ; growing on hard substances. 



Log. Rarasgate pier, liamsgate. 



Ohs. Independently of the interest attaching to this sponge 

 as nyAYiQiyoiLeucosolenia lacunosa^ Bk., it is still more inter- 

 esting as presenting a spiculation and structure which reveal 

 the nature of tlie " filiform spicules " and structure of the 

 fibres in some of the fossil Oalcispongiaj from the " Coral 

 Hag" of Faringdon in Berkshire, 



These spicules, although first represented by Zittel, in 1878, 

 in Feronella multidigitata (Abh. k. bayer. Akad. d. W. ii. 

 CI, Bd. xiii. 2 Abth. Taf, xii. fig. 3), were just afterwards, 

 that is in the same year, more particularly described and illus- 

 trated under the above name, viz. " filiform spicules," by 

 Sollas (' Annals,' 1878, voh ii. p. 356, pi. xiv. figs. 1-5) ; 

 and subsequently described by myself (' Annals,' 1883, vol, xi. 



P-22).. 



Until Ziltel had kmdly convinced me by a microscopic 

 preparation of Feronella multidigitata from the CretaceoUs 



