120 
NAUTILOIDEA. 
septum. The whorl,” he continues, “ was here a rapidly increas- 
ing cone, the abdomen [periphery], however, quit^s as gibbous as the 
dorsum, whereas in the adult the latter is the more prominent, the 
abdomen becoming deeply inflected. The termination of the whorl 
was very much flattened, so that from the side it had quite a 
pointed aspect, whereas an abdominal view showed it to be rounded 
at the extremity.” He adds that “ the whorls do not . . . touch 
at first. The tip of the cone is free for some distance before the 
involution brings the whorls in contact. No marks of a cicatrix 
were discernible.” 
In the initial part of the shell, as observed by M. de Koninck, 
the ventro-dorsal diameter exceeds the transverse, but as growth 
proceeds the reverse takes place, and the lateral diameter greatly 
exceeds the ventro-dorsal, while at the same time the fine longitu- 
dinal ridges disappear and leave only three keels on each side of 
the periphery, the outer one of which forms the edge of the umbi- 
licus. Another keel remains just inside the umbilicus, making 
altogether four on each side. 
All the keels have their edges finely crenulated, and on close 
examination it is found that these crcnulations or serrations arc 
caused by a number of minute, transversely elongated and slightly 
oblique nodes, of the same character as those described in Gyroc^ras 
serratum, de Kon., G. tesseJlatum, de Kon.,&c. The serrations entirely 
disappear when the last whorl is attained. A"ery fine lines of growth 
cover the whole surface of the shell. 
The septa number twenty-foui' in a volution ; they are shallow, 
and their sutures are strongly sigmoidal on the sides of the shell, 
bent backwards at the lateral angles, and forming a deep sinus upon 
the periphery. The body-chamber is large, occupying a little more 
than half of the last volution. The siphuncle is small and is 
situated a little above the centre. 
Remarhs. The first whorl of this species would be difficult to dis- 
tinguish from C. pingids, but the periphery remains convex in 
that species, whilst in C. Koninckii it becomes flattened and even 
slightly concave. The rate of increase is also more rapid in C. 
pinguis than in C. Koninclcii, and the septal sutures much more 
sigmoidal laterally and more strongly bent backwards in the latter 
than they are in the former. 
M. de Koninck expresses the opinion that Nautilus {Temnoclieilus') 
crenatus, M'Coy, cannot be regarded as identical with C. Koninckii, 
as supposed by Giebel because the keels in the latter are never 
^ Fauna der Vorwelt, 1852, Band iii. Abth. i. p. 173. 
