449 
included under this name. One is separated above as Zurphyceras 
Farnsworthi and the other below as Aphetoceras attenuatum. ‘The 
type is that figured by Billings, and this had the living chamber 
free and deviating strongly from the spiral. It was 91 mm. long 
on the dorsal surface and more than one-half of a volution in 
length when this measurement was applied to the coil of the preced- 
ing whorls. The siphuncle in the ephebic stage was propioventran 
and the septa much closer together than is usual in this genus. 
APHETOCERAS ATTENUATUM. 
LiruiTEs FaRNSworTHI, Bill. ( pars.) (op. cit., p. 21). 
Loc., Phillipsburg. 
This species is founded upon the specimen described by Billings 
on p. 21 of his Paleozoic Fossils as having first two whorls in con- 
tact and making a coil an inch across. These whorls are, however, 
not in contact on his specimen, if my drawing of this is correct. 
The specimen is of nearly the same size as the type of Aphetoceras 
Frarnsworthi, but one and a quarter volutions are free, so as to 
leave a gap of 8 mm. before the completion of the first quarter of 
the septate part of the eccentric volution, and at the end of the 
same this gap has increased to 13 mm., and in the next quarter, at 
the end of the living chamber, it is 25 mm. The departure of the 
free whorl of Farnsworthi increases, as shown in Billings’ drawing, 
in less than one-half of a volution to 40 mm. 
The septate part of the eccentric volution in this specimen is 
58 mm. long, the living chamber is 88 mm. long. The former 
would occupy about three-fourths of a volution if it followed a reg- 
ular open spiral curve, and the latter would be about one-half of a 
volution, estimated in the same way. 
The septa are similar to those of Hurnsworthi. The fragment of 
the siphuncle observable in the neanic stage changes in the length 
of 1o mm. from nearly subventran to propioventran. 
Deltoceras,* n. g. 
The shells of this group resemble those of Aphetoceras, but are 
just one grade more complicated. The whorls are similar in section, 
but grow more rapidly in the ventro-dorsal diameters, the siphuncles 
. in some species are very large and ventral. The sutures are simi- 
* Agdtog, ascroll. 
PROC. AMER. PHILOS, SOC. XXXII. 142. 3E. PRINTED JUNE 27, 1894. 
