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with opercula, and that their internal structure was materially different 
from that of any orthoceratites which had been hitherto described*. 
These shells, Plate VIII. Fig. 1 and 5, undoubtedly require to be 
considered as of a distinct genus from orthoceratites. Like orthoce- 
ratites, they are fossil, testaceous, conical tubes, more or less approach- 
ing to a cylindrical form, being sometimes straight and sometimes 
curved, and internally divided into numerous chambers by horizontal 
septa : but, unlike the orthoceratites, they do not appear to be provided 
with a syphon ; the functions of this part having been perhaps per- 
formed by two converging ridges, which, at no great distance from 
each other, proceed from the sides of the cavity along its whole length. 
Soon after their origin, these ridges suddenly contract ; and then, gra- 
dually becoming more tumid, terminate in rounded edges, at about a 
third of an inch from the sides. The gutter which is formed between 
these ridges is generally, like the rest of the cavity, divided into cham- 
bers by numerous transverse septa. Picot describes what he conceives 
to be the remains of a siphunculus, in two specimens ; but the appear- 
ances do not appear to be such as to warrant the supposition. The 
representation of this specimen is, however, here copied from Plate II. 
Fig. 2, of Picot’s work; Plate VIII. Fig. 5, a, marking the part in 
which the siphunculus is supposed to have existed. 
The Baron Picot observes, that in several specimens the gutter, or 
space between the ridges, is entirely empty, or free from septa ; but 
very properly remarks, that this must not be relied on as a specific dis- 
tinction ; since it is probable, that in its original state it was furnished 
with septa. Having very fortunately obtained some specimens of this 
curious and interesting fossil, and having amongst them two specimens, 
in which this part was thus empty, I carefully examined them, and was 
surprised at not finding the least trace of the adhesions of septa on its 
* Philippi Picot de la Peirouse de novis quibusdam Orthoceratitum, &c. Dissefta- 
tiuncula. Page 4. 
