621 
PratEs Ti: 
Figs. 1-7. Deroceras (Amm.) planicosta, Hyatt, Embryology Ceph. Bult. 
Mus. Comp. Zoblogy, iii, No. 5, Pls. i and il. 
Fig. 1,side view of nepionic and neanic stages, X 80 diameters. Fig. 2, sec- 
tion of another specimen, X 21.5 diameters; B,protoconch. Fig. 3, centre of same, 
enlarged to show the umbilical perforation (U) as it occurs in Ammonitinz and most 
of the Goniatitinz. Fig. 4, protoconch and first volution with ananepionic first sep- 
tum; x, probably sutures of the first septum on the dorsum seen through the whorl ; 
X 80.* Fig. 5, side view of protoconch, ananepionic first septum I e, and meta- 
nepionic septa, 2 e, 3 e; D, shell; B,naked cast of interior of protoconch; y, coni- 
cal appendage of czecum seen through the whorl. Fig. 6, section of same speci- 
men exposing interior of the protoconch (y), the conical czecal prolongation, and 
the fundus of the cecum and the first two septa, S, being the neck of the small 
siphuncle at the third septum, which is broken off. Fig. 7, thin section of caecum 
and part of conch with four septa, showing formation of czecum by the first septum 
I e, the composition of the cecal prolongation y, the neck of the caecum formed 
by the second septum 2 e, the siphon begun by the third septum and continued 
by the fourth, both of which have funnels directed apically as in Nautiloids; S/, 
organic deposit in the interior; S/’, inner layer; S//’, wall of siphuncle; X 317 
diameters. 
Fig. 8. Deroceras (42goc.) planicosta, Branco, Paleontographica, xxvii, Pl. x, 
showing protoconch from a different point of view and less magnified. Fig. 9, 
same, with first to fourth sutures showing. 
Fig. 10. Pleuroceras (Amaltheus) spinatum, Branco (zé2d.), Pl. xiii, enlarged, 
showing the interior of the protoconch; the septa of first whorl are cut exposing 
the cecum. The septa are all convex and strictly ammonitoidal except the 
first, which is concave, as in Nautiloids and the adults of Mimoceras, Anar- 
cestes and Agoniatites among Ammonoids of the Silurian period. 
Figs. 11 and 12. Crioceras Studeri, Branco (7b7d.), Pl. xiii, enlarged, showing 
the coiled young of this uncoiled degenerate form. + 
Figs. 13-18. Baculites compressus, Brown, Proc. Acad, Sci. Phila., 1891, p. 1595 
1892, p. 136, Pl. ix. Fig. 13, enlarged young shell in the neanic stage, showing 
the lines of growth, aperture and rostrum on the ventralside. Fig. 14, front view 
of shell in the paranepionic substage; the siphuncle is not subventran. Fig. 15, 
front view with the two metanepionic and four paranepionic sutures, those with a 
siphonal lobe divided by a siphonal saddle being paranepionic in age. Figs. 16 
and 17, front and side views, with restoration of the ananepionic substage. Fig. 
18, side view of Fig. 15. 
Figs. 19-21. Apex from the front and side and sutures of Mautzlus Clemen- 
tinus, after Branco, of. cz¢., xxvii, Pl. ix. 
Fig. 22. Sutures of Nautilus deslongchampsianus, after Branco, (2dzd.), 
Plas 
* This figure has no number. 
+ See also for similar forms Pl. xi, Figs, 40, 41. 
