N anno, a N~ew Cephalopodan Type. — Clarke. 207 
original organic deposit; the internal cavity is filled with the 
mud of the sediment. Cross-sections of the cone in both direc- 
tions indicate that this is not a simple body, but is composed 
of at least two invaginated and consolidated sheaths, the line 
between which is represented only by a faint streak or differ- 
ence in the texture. This evidence, though obscure, is indis- 
putable that the sipho enclosed or was composed of si phonal 
sheaths, as in Pilot-eras, Vaginoceras and Endpceras. The 
sections afford no evidence of an endosiphon <»r tube connect- 
ing the apices of these sheaths. 
The addition of the septate portion of the shell gives the spe- 
cies a fusiform and symmetrical appearance, broadest below 
the aperture, the sipho seeming to extend nearly, if not quite, 
the entire length of the shell. The septa are gently and reg- 
ularly concave over most of their surface, but abruptly de- 
flected immediately about the sipho. There were apparently 
about twelve in the length of the shell as preserved. The first 
septum seems not to conform to the contracted surface of the 
cone, which has a much greater obliquity, and there thus ap- 
pears to be an irregular wedge-shaped cavity between these 
two surfaces, but there is no evidence whatsoever that the 
conical end of the sipho was in any way involved in this cav- 
ity except at its upper surface. 
The apical solid cone w;is unquestionably external, except 
so far as ensheathed by a nitre coating or film of the shell- 
tube. 
All the specimens indicate that these shells were of small 
size; a nearly complete sipho has a length of :5(> mm.: it > 
greatest width is at ID mm. from the apes and measures 10 
mm. in major, and 8.5 mm. in minor axis; its apcrtural diam- 
eters are 8 and H mm. Another and more splendid specimen 
measures 40 mm. in length and is broken ;it the aperture. 
Here the length of the apical cone is '12 mm. The most com- 
plete example has a length of 58 mm.: the apical cone meas- 
ures 15 mm.; the entire diameter of the shell is IK mm. at its 
widest part and 16 mm. at or near the aperture. 
The shells thus described represent but one species, which it 
is proposed to term Nanno aulema. Prom their structure it 
is evident that their relations are closest to Piloceras, but 
