12 
SILURIAN 
the thick-edged compressed nacreous tubes which first received 
the above name, and which very possibly are not annelides 
at all. 
Locality .—Milam Glacier. Chorhoti. (Nos. 933, 1754.) 
MOLLUSCA CEPHALOPODA. 
These are but few, but they remind us, by their general 
characters, of those of other Silurian regions. This may 
certainly be said of the species of the genus Orthoceras. 
The 0. Kemas is exactly like a common Ludlow rock 
fossil. The species of Lituites can scarcely be otherwise 
than from the same Silurian group, but it is right to 
say there is some doubt of the formation from which the 
Nautilus was obtained. 
It is from a loose fragment of black limestone at Gunes- 
gunga, and may have been derived from younger beds—though 
this does not seem likely. To avoid mixing it with the other 
fossils, to which, nevertheless, we think it belongs, it will be 
described first. 
NAUTILUS ? INVOLYENS- 
Plate 2, fig. 3. 
N. involutus, compressus, anfractibus 3 latis, ad umbllcum par- 
vum valde rotundatis, lateribus planis, angulis externis obtusis, dorso 
piano. Septa obliqua conferta, lente curva, nisi ad umbilicum abrupte 
flexa. 
The name Nautilus is retained for this obscure fossil rather 
as an indication of its possibly belonging to a newer set of 
rocks. It is too involute and Nautiloid for any Silurian 
Lituites or allied genus known to me, but is not unlike some 
of the species of iDiscites, a sub-genus of Nautilus common in 
carboniferous strata. 
Our specimen has a diameter of 2j inches, and has three 
compressed whorls—perhaps a minute fourth. The outer 
whorl is nearly four times as wide as the next succeeding, and 
