164 
XAUTILOIDEA. 
row of tubercles along the edge of the abdomen on either side. 
The sutures have deep Y-shaped ventral lobes, deep lateral, and 
dorsal lobes; no annular [ = internal] lobes in any species observed. 
The dorsum is frequently gibbous, and has an impressed zone only 
in the more compressed and involute species. Centroceras tetra- 
gonum, d’Arch. de Yern. (Trans. Geol. Soc. 1842, ser. ii. vol. vi. 
p. 351, pi. xxxi. jff. 3, 3a), has young which are identical with 
adults of Temnocheilus, and adults similar to those of typical Centro- 
ceras, but less compressed.” 
Type, Nautilus {Discites) Marcellensis, Hall ' . 
Nemarks. It is to be regretted that Professor Hyatt has not indi- 
cated what species he would include in this series, besides the two 
he has mentioned. There appear, however, to be very few forms 
that could be properly referred to Centroceras. To those above 
named I would add the Ggroceras hinodosum of G. & F. Sand- 
berger, which is evidently very closely allied to C. tetragonum, 
having the sharply angular nodose whorls and ventral siphuncle 
characteristic of that species. 
The remarkable feature in this genus is the quadrate form of the 
shell in section and the closeness of the septa. All the European 
examples of it known are fragmentary. 
Temnocheilus (Centroceras) tetragonus, d’Archiac and 
de Yerneuil, sp. 
1842. Cyrthoceratites tetragonus, d'Archiac and de Yerneuil {Spirula 
dorsata, Bonn Museum), Trans. Geol. Soc. ser. ii. vol. vi. p. 351, 
pL xxxi. ff. 3, 3 a. 
1853. Cyrtoceratites tetragonus, Steininger, Geogn. Beschreib. der 
Eifel, p. 41. 
1876. Cyrtoceras tetragonum, F. Rcemer, Lethsea geognostica, Theil i. 
Leth. palaeozoica, Atlas, Taf. xxx. ff. 4 a, 4 h. 
1883. Centroceras tetragonum, Hyatt, Proc. Boston Soc. Nat. Hist, 
vol. xxii. p. 284. 
Sp. Char. “ Shell quadrangular, slightly arched, presenting longi- 
tudinal tubercular folds, with equal interspaces, upon the two outer 
angles. Inner angles simple. Septa numerous, near together, 
with undulated edges, concave on each surface and rising toward 
the aperture at their passage over the angles. Siphon small, sub- 
Geol. Surv. of New York, Palseont. vol. v. pt. ii. p. 428, pi. Ixv. ff. 1, 2, 
pi. cix. ff. 9-12. Also ibid.. Supplement (Cephalopoda), 1888, (contained in 
vol. vii. of the same work, 1888), by C. E. Beecher, p. 39, pi. cxxvi. f. 6, which 
shows the hollowed-out periphery and ventral siphuncle of this species. 
