20 
EoPER, on Biddulphia. 
membrane^ which is reticulate or punctate, forms the same 
peculiar projection beyond the suture of the valve, which is, 
I believe, characteristic alone of Biddulphia and its imme- 
diate allies ; and though Professor Smith lays some stress on 
the orbicular outline as a distinctive character,"^ we have 
seen that this is also to be found in B. turgida and B. IcBvis, 
and certainly forms no good ground for its separation from the 
present genus. Professor Smith appears himself to have 
had some doubts, as notwithstanding the argument he adduces 
for its present position, I find it is figured in the plate, 
No. Ixii, as Biddulphia radiatus ; and I have little doubt 
that a careful examination of a larger number of specimens 
would have induced him to adopt the generic position I now 
assign it. 
It appears to be by no means common on our coasts, as 
though I meet with it in tolerable abundance in some gather- 
ings from the coast of Norfolk, of Col. Baddeley^s, and in 
most gatherings from the lower part of the Thames, I have 
not seen specimens from any other parts of England, and 
I do not see any form in Ehrenberg^s numerous figures 
with which it can be compared. 
It is readily distinguished from Biddulphia turgida and B. 
Imvis by its reticulated valves, and from all other species by 
its orbicular outline. 
The following list contains all the other species I have 
met with, which, for want of specimens or good specific cha- 
racters and figures, I can only refer doubtfully to known 
forms : 
Bid.? lunata. Ehr. B. Proc, 1844, p. 77,^ 
Yirginia 
Bid. ? GIGAS. Ibid., p. 265, Bermuda 
Denticella l^vis. Ibid., p. 201, Antarctic ) = Bid. 
Sea . 
Odontella l^vis. Kiitz. Spec. Alg., p. 136, 
ditto . . . .y 
Bid. elongata. Meneffh., quoted in Kiitz. i t,-/ i -l n 9 
Spec. Alg., p. 1 37 . . } = ^^^^'^'^^^ • 
Denticella dueia. Bailey, Soundings, t. i, \ 
f. 57 . 
Odontella sub^qua. Kiitz. Bac., t.viii,f.4,5 I = Bid. aurita? 
Odontella obtusa. Ibid., t. viii, f. 1 — 3, 
6—8 ... .J 
Zygoceros baljsna. Ehr. B. Pro., 1853, p.-. These forms being with- 
529, and Microg., t. xxxv, A.xxiii, f. 17 I out angular processes, 
Zygoceros ? ATJSTEALis. Ehr. Ber. Proc, r should probably be 
1844, p. 205 . . .J united with Terpsinoe. 
* Smith's 'Syn.,' vol. ii, p. 47. 
