445 
EURYSTOMITES UNDATUM. 
NavuTILus unpDATuS, Hall (Padé. Mew York, i, p. 52, Pl. xiii and 
xlil dzs). 
Loc., Poland, Herkimer county, N. Y., Black River Limestone. 
Blo, Figs. 1,2. 
This species has much broader whorls in the young than in 
Eurystomites of the Quebec faunas. ‘The position and size of the 
siphuncle, the large umbilical perforations and the sutures and the 
flattened abdomen of the adult stage and comparison with the 
heavily costated forms like D¢scoceras antiquissimum and others 
show that this shell is probably a member of the genus Eurysto- 
mites. 
The nepionic stage has a very large umbilical perforation and in 
correlation with this the whorl has a rounded dorsum at this age. 
The metanepionic substage has a broadly elliptical form and sub- 
ventran siphuncle ; the paranepionic, on account of the rapid trans- 
verse growth, has a subdigonal whorl, as shown in Fig. 2, Pl. v. 
The shell does not increase so fast transversely in the neanic stage 
and the whorl becomes rounder, a slight contact furrow appearing 
when the whorls come in contact, and the living chamber at this 
age is less than one-half of a volution in length. Light costations 
also appear in this substage, but the nepionic whorl is smooth with 
the exception of strong lines of growth. The abdomen becomes 
flattened in the paraneanic substage, and the sutures show slight, 
ventral lobes and very slight lateral lobes. 
The siphuncle is propioventran in the paranepionic substage and 
neanic stage. The costations become stronger in the paraneanic 
substage but are reflected on casts only to a very slight extent. 
The young are, however, quite variable, and the figures, Pl. v, 
give probably an extreme form so far as the retention of the broad 
subdigonal form is concerned. In other varieties or species, for I 
think ‘there are several species usually placed under this name, the 
sides and venter become slightly flattened in the metaneanic sub- 
stage, or even before this. In the specimen figured this change 
had not yet taken place, although the shell was in the metaneanic 
substage. 
The aperture in this specimen flared out laterally, but is removed 
in the section-Big.. 2, Pl. -v. 
Slight, foldlike costz are better developed in the ephebic stage, 
