the Greensand compared loith those of existing Species. 131 



this half, the bkintcd extremity varying also in form from that 

 of being- simply rounded in fig. 78 to pin-head-like inflation 

 as in fig. 77. 



Here, then, we also come upon the characteristic form of the 

 spicule in Donatia, Gri'^J {Tethya lyncurium)^ and its like ; but, 

 as before stated, in the absence of the large stellates peculiar 

 to the existing species, the acuate spicule alone is a useless 

 indication. 



Lastly, we arrive at the smaller spicules of the deposit, re- 

 presented in PL IX. ; and beginning with fig. 43, we at once 

 recognize its bihamate pointed form, which association leads us 

 to connect with the Esperiadce. But where are the little ancho- 

 rate spicules which in the existing species always accompany 

 it in a still more minute form ? These also are absent, and, 

 from their minuteness and delicate forms, may have disap- 

 peared under the destructive and dissipating influences before 

 mentioned. Still, for future reference, this spicule must also 

 be named ; and hence I would call it Esjierites haldonensis. 



It is six times as large as that of the great branching Es- 

 peria of the deep sea, from which I have been kindly provided 

 with a small portion for reference by Dr. Carpenter ; and this, 

 again, possesses the largest bihamate of any existing species 

 with which I am at present acquainted. Yet the fossil speci- 

 men is C-like, more or less contort, and in all other respects, 

 as will be seen by the figure, exactly like the bihamate of the 

 present day. It was first brought to my notice by Mr. Vicary, 

 who found it in the Haldon deposit, after which I obtained 

 several myself in specimens of this deposit. They are all about 

 the same length, viz. l-37th of an inch, while those of the dee])- 

 sea species only average 1 -222nd of an inch ; so that Avhile 

 the former can be well seen Vv' ith a simple lens of low power, 

 the latter can only be seen with the |-incli combination of a 

 microscope. 



Still larger is another but sigmoid contort form of this (?) spi- 

 cule, viz. fig. 79, of which one specimen only has been found, 

 and that, too, by Mr. Vicary, in the Haldon deposit. Its 

 gigantic size, being 1-1 7th of an inch long, and of proportionate 

 thickness, makes one almost doubt its identification with the 

 bihamates. However, as it is, so it is represented in the figure, 

 where its remarkable size and form show that it should also 

 have a name for distinction's sake. Hence we will call this 

 Esperites giganteus. 



It is impossible to confound the bihamate spicule of a sponge 

 with that of an echinoderm, since the latter, as in Echinus 

 sphcereus^ to which Dr. Bowerbank alludes (Brit. Spong. vol. i. 

 p. 44), is not only vastly more minute than our smaller fossil 



