= 
PORIFERA OF THE L.M.B.C. DISTRICT. 219 
sz.* For an exhausting account of this comedy of errors I 
refer to Leidy’s recent paper “The Boring-Sponge, Cleona +” 
Leidy, in his paper, also discusses the question whether 
the Cliona sulphureu, Desor, of the American coast, which 
is found both boring and massive, might be ideutical with 
Cliona celata, Grant, of Europe. He finds that the two 
forms agree in all respects except two. Hancock? had 
stated that in Cliona celata, Grant, hexagonal siliceous 
granules are found on the surface of the sponge, by which 
the latter is able to work out the cavities it inhabits. 
Leidy says he has not been able to detect those granules 
in the American sponge. The second difficulty is: “‘ Grant, 
Hancock, Bowerbank, and Lieberkthn give as the size of 
the spicules of Cloona celata about J; of an inch, while in all 
our (‘i.e. American’) forms of Cliona, in the oyster and 
clam, and in the largest massive varieties, the size of the 
spicules is only about = of an inch.” 
The first difficulty about the hexagonal granules has 
been solved by Topsent.§ He considers them as broken 
pieces of the prismatic layer of the perforated shell, perhaps 
intermixed with grains of quartz. In regard to the second 
difficulty, Topsent remarks that the difference in size of 
spicules cannot be of much value, as he himself has ob- 
served spicules from 0°18 mm. to 0°35 mm. in length. On 
page 217 I gave as the length of the spicules 0°315 mm. As 
,imch is equal to 0°508 mm., and J inch is equal to 0°317 
mm., we see that Topsent’s and my own observations agree 
with Leidy’s measurements as exactly as one could expect: 
* Bowerbank, ‘‘ British Spongiadze,” vol. ii., p. 354 ; vol. iii., pl. Ixiv. 
+ In. ‘“‘ Pro. Acad. Nat. Sciences, Philadelphia,” part i., January—April, 
1889, p. 70. 
£ Albany Hancock, ‘‘ On the excavating power of certain Sponges belong- 
ing to the genus Cliona,” 1849. 
§ Emile Topsent, ‘‘ Cliona celata ou Cliona su’phurea? Bulletin de la 
Société Zoologique de France,” 1889, p. 351. 
