NEW DIATOMS. 
69 
12. Rhoicosigma Antillarum. a.— Median line sigmoid very 
elevated on the one half of the valve, where it forms a crest im- 
pressed on the other half. Striae distinct, transverse, 14-15 in. ’01 
mm. L. *425 mm. Virgin Islands (rare). 
13. Plagiogramma (decussatum var. ?) Antillarum. Cl.— Valve 
elliptical, extremities broadly rounded ; interior septae 4, 2 near the 
ends, 2 in the centre; puncta in transverse and longitudinal rows ; 
transverse, 8-9 in. *01 mm. L. 'OT-’OS mm. Virgin Islands 
(rare). P. caribceum, Cl. Outline resembling P. lyratum, Gre ville. 
Interior septae 4, 2 near the ends, 2 in the middle. The two 
central septae are connected with the end septse by a strong median 
rib and by two others following the margin of the valve. Puncta 
or granules arranged in distinct parallel transverse rows, 8-9 in., 
*01 mm. L. *012-*088 mm. Virgin Islands. 
14. P. attenuatum. Cl. — Valve small, lanceolate acute ends, 
slightly rounded. Septae 2 central and 2 near the ends. The two 
central septse form, in the middle, a rounded quadrangular annulus, 
puncta arranged in parallel transverse 10 in. *01 mm. L. *05 
mm. St. Bartholomew (very rare). 
15. Nitzschia (Sigma var. ?) valida. Cl. <Sf Grun. — Valves slender, 
almost straight, sometimes more or less sigmoid, with cuneate ends. 
Punctse about 4 in. *01 mm. Strise distinct, 18 in. *01 mm. Vir- 
gin Islands (very rare). Campeche Bay, Grunow. Sulu Archi- 
pelago, Kitton. 
16. N. (Jelineckii var.) acuta. Cl. - This form greatly resembles 
N. Jelineckii of Grunow (=j V. decora , Kitton. Grunow’s sp. 
name having the priority, mine must be deleted), but its ends are 
cuneated and pointed. The ends are connected by a very sharp 
and visible keel. Strise distinct, 11 in. *01 mm. Virgin Islands 
(not rare). 
17. N. (longissimus var. ?) curvirostris. Cl. — (This form only 
differs from N. longissima by the horns being curved in the same 
direction, and from N. ventricosa by the fineness of the strise ; the 
curvature is of no distinctive value ; in mounting selected specimens 
of N. ventricosa , the horns may be placed in any position. — F. K.) 
St. Bartholomew (only one specimen). 
18. N. (Perrya) Weissflogii. Grunow • — Valves resembling a 
long and very narrow boat, with a sharp keel, smooth or covered 
with minute, irregularly-scattered granules, which form coherent 
longitudinal rows only on the keel, and near the margin of the 
valve; the keel is besides marked by a row of sharp transverse 
bars, which (as in all other Nitzschese) lie in the interior side of 
the valve, and are fastened to each side of it. L. *155-*32 mm. 
Campeche Bay, Grunow. Colon, Kitton. 
Var. a , subglabra , valves almost smooth. 
Var . /3, sparsa , valves covered with irregularly scattered minute 
granules. 
