75 
Remarks on the Marine DIAT0MACE.E/b^^7^ri at Hong Kong^ 
ivith Descriptions of neiv Species. By Henry Scott 
Lauder,, Assistant-Surgeon, Eoyal Navy; with Notes by 
J. Ralfs^ Esq. 
(Read Eeb. 10th, 1864.) 
The Diatomacese are generally very abundant in Hong 
Kong harbour ; so abundant, indeed, that in a few minutes, 
by means of a small muslin towing-net, a jelly-like mass, 
about the size of a walnut, is obtained, consisting of about 
equal parts of diatoms and Estomasbtarca, &c. It is worthy 
of notice that, in different months, different forms are pre- 
valent, giving distinct characters to the gatherings. For 
instance, in January, very few diatoms are obtained. 
In February the Coscinodiscese are most plentiful. In 
March and April numerous species of Rhizosolenia and 
Chsetoceros make their appearance, and about the end of 
April nearly every diatom (except a few Coscinodiscese) has 
disappeared, being replaced by an increase of animal life, 
and a species of Oscillatorise. 
As species of Chsetoceros are the most fi^equent in the 
gathering, and at the same time very curious, I shall attempt 
their description in this paper. 
Genus ClicEtoceros, Ehr., frustules smooth or minutely 
punctated, united with the adjacent ones by the interlacing 
of awns proceeding from. the frustule. 
Frustules in the front view, quadrangular generally, with 
concave valves, leaving a fenestra of a size and shape vary- 
ing in different species between the contiguous frustules, 
with awns arising from the angles, or from the lateral sur- 
face of the valve. The awns are usually many times longer 
than the breadth of the frustule, tubular, circular^ quadran- 
gular, or hexagonal; cellulose, spinous, or with bead-like 
dots. I have seen none indubitably smooth, although some 
are so delicate that no markings can be detected on them. 
Length of filament varying according to age, from two or 
three frustules to more than a hundred. In perfect fila- 
ments the awns of the terminal valves, that is to say, the two 
valves of the original frustule produced from the Sporan- 
gium, are usually shorter and stouter than the others, and 
often differ from them in shape. 
The mode of growth in Chsetoceros is similar to that of 
the Biddulphise. The endochrome increases in quantity, 
then shrinks away from the sides, generally forming a central 
