595 
Pl. xii, and in Fig. 1, Pl. xiii, which is the reverse-of that of Fig. 
30, but enlarged two diameters. The presence of an annular lobe 
is noted as it appeared in the specimen, but this part was covered 
by remnants of the nacreous layer and it was not positively defined. 
The dorsal furrow began between the first and second septum and 
is faintly shaded in Fig. 1, Pl. xiii. The dorsal sutures were cov- 
ered except as far as represented. The side view, Pl. xii, Fig. 2, 
shows these sutures, so far as seen, the last two in this figure being 
the first two of Fig. 29, Pl. xii. 
The broad costze of the genus made their appearance in the ana- 
neanic substage at the same time that the septa approximate and 
the zone of contact is formed. 
It will be observed that the costz are broader at first than they 
are in later age even in this figure, showing that growth was more 
rapid at first as in the development of the septa. 
Lutrephoceras,* n. g. 
This genus includes these forms like the type Lu¢rephoceras 
Dekayi, which have globose ananepionic substages, increasing subse- 
quently with great rapidity in all their diameters. The ana- and 
metanepionic substages are highly tachygenic and these shells have 
very small, and often hardly perceptible and much flattened, um- 
bilical perforations. ‘The siphuncles are subdorsan from the apex 
through the nepionic stage in some species, in others this position 
is not maintained, but the siphuncle is generally in later stages 
near the dorsum and in the ephebic stages it is dorsad of the 
centre. 
The nepionic stage has longitudinal ridges and transverse bands, 
the former disappearing in adults which are smooth. 
The form of the whorl in section is nephritic from an early age 
and changes but little throughout life. 
The sutures are almost straight, having but slight ventral lobes, 
broad ventro-lateral saddles, lobes on the umbilical zones and deep 
lobes in the zone of impression. There are no annular lobes at 
any stage of development. 
* Evutpegys, clasping around. 
