22 
(jREviLLE^ on New Diatoms. 
Whether,, therefore, Ehrenberg's genus, or Creswellia, as 
proposed by Professor Walker-Arnott and myself, be pre- 
ferred, one portion of the Pyxidiculce may be regarded as 
satisfactorily disposed of. 
Two other genera of Pyxidiculm — -Pyxidicula and Dictyo- 
pyxis of Ehrenberg — still remain in a very confused state. In- 
deed, it is probable that the perfect condition of most of the 
species is unknown. Mr. Ralfs considered it desirable to re- 
tain Dictyopywis as a sub-genus or section of Pyxidicula^ until 
some of the species were better known. His generic cha- 
racter for the whole is, "frustules simple or binately con- 
joined, free or adnate, bivalved ; central portion obsolete ; 
valves very convex." The two sections being — 1. Frustules 
smooth, or minutely punctate {Pyxidicula), 2. Frustules 
cellulose {Diciyopyxis) . While recently engaged in the 
examination of Dr. Macrae^s slides, I was so fortunate as to 
find two examples of a Diciyopyxis with the frustules con- 
nected, and consequently I have it in my power to offer a 
more definite character of that genus, which will now be 
placed in as satisfactory a position as Creswellia. 
It remains to be seen, however, how many of the dia- 
toms at present referred to it will exhibit the same struc- 
ture. 
Diciyopyxis brevis, n. sp., Grev. — Valves equal, cylindrical, 
much shorter than they are broad; junction-surfaces some- 
what convex; celhiles hexagonal, very small, 10 in '001". 
(PI. II, fig. 2.) 
Hab. Andaman Islands. Ceylon, Dr. Macrae. 
This species appears to differ very decidedly from those 
already described. It is remarkable for the shortness of the 
frustules ; so that if one of the valves alone be taken, the 
length is scarcely more than half the breadth. The cellules, 
small as they are, are exquisitely regular and hexagonal. 
The frustules are connected in the same manner as in 
Orthosira marina ; only as the junction-surfaces are some- 
what convex instead of plane, they occupy less space. Side 
views of the valve are frequent. 
EuPODISCUc^. 
Eupodiscus Jonesianus, n. sp., Grev.-^ — Disc pale, with 
closely radiating lines of minute puncta; processes oblong, 
submarginal. Breadth -0064". (PI. II, fig. 3.) 
Hab. Guano; locality unknown; Dr. Macrae. 
A species remarkable for its minute structure^ presenting 
in this respect the greatest possible contrast to E. Argus 
