THE WELL-BORING AT RICHMOND, SURREY. 783 
without exception, is shown by the fact that many of the calcareous 
sponges discovered by the Challenger Expedition are from depths of 
100 to 150 fathoms, and one species occurred at a depth of 450 
fathoms. 
EXPLANATION OF PLATE XXXV. 
Figs. 1, la-d. Inobolia micula, Hinde. 
1. An average specimen, natural size. 
la. The same, enlarged four times, showing the disposition of the fibres 
on the surface. 
16, A portion of the interior fibre, enlarged twenty-eight times, showing 
traces of the component spicules. The fibres are imbedded in a 
matrix of crystalline calcite, in which are grains of iron-pyrites. 
Drawn from a transparent microscopic section. 
1c. A small portion of the interior fibre, enlarged seventy-five times, 
showing a large three-rayed axial spicule, and the minute filiform 
spicules surrounding it. 
1d. A portion of the dermal layer, showing some of its component spi- 
cules, enlarged twenty-eight times. A portion of the surface-fibre 
is Shown in the upper part of the figure. Drawn by reflected light. 
2, 2a. Peronella nana, Hinde. Natural size and enlarged four times. 
3,34. Blastinia cristata, Hinde. Natural size and enlarged four times. 
36. The same. <A portion of the interior fibre, enlarged twenty-eight 
times. Drawn from a transparent microscopic section. 
4,4a. Blastinia pygmea, Hinde. Natural size and enlarged four times. 
5, 5a. Oculospongia minuta, Hinde. Natural size and enlarged four 
times. Showing the disposition of the fibres and the oscules. A 
small Serpula is attached to the surface of the specimen. ; 
56. The same. A portion of the interior fibre showing the component 
spicules. Enlarged seventy-five times. 
The specimens are all from Jurassic strata penetrated in the well-boring at 
Richmond, Surrey, at 1205 feet beneath the surface. 
