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THE VOYAGE OF H.M.S. CHALLENGER. 
Spicules. — I. Megascleres. 1, Desma, epirabd curved, semicircular, or straight or 
triradiate, rarely quadriradiate, bearing spined tubercles, in the curved forms on the convex 
side ; zygosis general. A semicircular form measured O’ 24 mm. along the diameter, and 
0’038 mm. in thickness ; a more or less straight form 0’38 mm. in length ; crepidial axis 
0’04 mm. in length. 2. Rhahdus, 0*0065 mm. in diameter, length and nature of ter- 
mination not determined. 
Colour. — In the dried state, greyish-white. Size, 18 mm. in diameter by 20 mm. iu 
height. 
Habitat. — Barbados; depth, 100 fathoms. Havanna; depth, 292 fathoms. 
Genus 7. Tremaulidium, 0. Schmidt. 
Diagnosis included in the specific description. 
Tremaulidium geminum, 0. Schmidt. 
Tremaulidium geminum, 0. Schmidt, Spong. Meerb. Mexico, p. 31, pL ii. figs. \a-l, fig. 2; pi. iv. 
figs. 1, 2, 1879. 
Sponge. — Irregular, with a flat base, incrusting, produced into vertical conical 
processes, with rounded or compressed chisel-like ends ; traversed by numerous vertical 
tubes ; surface covered with a very finely ridged outer layer (cuticula ?), 
Spicules. — Desma and rhabdus. 
Habitat. — Lat. 25° 33' N., long. 83° 1' W. ; depth, 131 fathoms. 
Remarhs. — This sponge, which I have not seen, is possibly nearly related to 
Siphonidium ramosum. 
Genus 8. Leiodermatium, 0. Schmidt. 
Azoricidm of vasiform shape, with comparatively large oscules situated on the outer 
surface ; pores distributed over the inner surface. 
Leiodermatium lynceus, 0. Schmidt. 
Leiodermatium lynceus, O. Schmidt, Spong. Atlant. Gebiet., p. 22, pi. iii. fig. 2, 1870. 
„ „ Carter, Ann. and Mag. Nat. Hist., ser. 4, vol. xii. p. 439, 1873. 
„ „ Zittel, Abhandl. d. k. baier. Akad. d. Wiss., pp. 103, 122, pi. i. fig. 5, 
1878. 
Sponge. — An irregularly curved plate or hollow cylinder, with deeply incised margin. 
Oscules circular, 0*5 to 0’75 mm. in diameter, opening on the summit of quite flat 
