RoPER^ on Biddulphia. 15 
time that its hairiness resembles Tetrachseta^ the Triceratium 
spinosum of Bailey. The distinctly cellular appearance of the 
surface is, however_, sufficient evidence that the present form 
is distinct from the B. ursina, and as I have met with it in 
three localities, and with strong similarity in structure, I 
think it may safely be considered a good and well-marked 
species. 
The variety /3, I at one time thought might be a distinct 
species, as, although agreeing in form, the reticulations of the 
valve are much smaller, and the processes shorter, than in 
the typical valve; but I have since met with intermediate 
specimens that are sufficient to induce me to include it as a 
variety of the present species, and should have adapted the 
characters to include it, had it not been confined to one 
gathering, and may therefore be the result of some local 
variation. 
9. Biddulphia tuinida, Ehrenberg (sp.) 
Valve orbicular-lanceolate, with minute reticulations 
radiating from the centre, and two or three curved sub- 
marginal spines; processes rather hyaline, slightly capitate, 
and rising abruptly from the surface of the valves which are 
subglobose on the front view. (Plate II, figs. 18, 19.) 
Marine ? Gomera, one of the Canary Islands ; Californian 
guano. Roper. 
Si/n. Denticella tumida? Ehr. Ber. Pro., 1844, p. 266. 
Odontella tumida. Kiitz. Sp. Alg,, 1849, p. 137. 
This species I first met with in some slides received from 
Mr. Topping, said to be from Gomera, and I conclude 
therefore marine. Ehrenberg has described a form from 
Bermuda under the name of Denticella tumida as " Testulse 
turgidss (subglobosse) septis lobisque destitutse, superficie 
subtilissime punctata, tubuiis finis, setisque totidem utrinque 
longe exsertis and although I can find no figure, and have 
not been successful . in meeting with any species in the 
Bermuda slides I have examined, that agrees with this 
description, I think the present form so nearly accords with 
his specific characters, that I am justified in adopting his 
name. 
The peculiar subglobose form of the valves is sufficient 
alone in the perfect frustule to distinguish it from all the 
other species of the genus. The detached valves have 
somewhat the form of those of B. rhombus, and the spines 
are similarly placed, but it is much smaller, less apiculate, 
and the processes more hyaline and more turgid at the base. 
The markings on the surface of the valve, with a magnifying 
