140 
NAFTILOIDEA. 
no regularity whatever in the distances at which they occur even in 
the same individual. They often occur quite close together, some- 
times three or four of them being ensheathed within each other ; 
and others again will have from 10 to 20 inches between them ; 
and I have seen examples of the shell from 2 to 4 feet long without 
a trace of a sheath.” ^ 
In the distance of the septa and proportionate size of the siphunclo 
this species resembles Endoceras belerrmitiforme, Holm {ante, p. 130, 
footnote) ; but the septa in the latter are as distant in the earlier as 
in the later stages of the growth of the shell, which is not the case 
in the present species. The rare preservation of the apical extremity 
of these long and finely pointed shells will always make any charac- 
ters founded upon the form of the apex but seldom available for 
purposes of specific distinction ; and indeed such structures, connected, 
as they admittedly are, with the embryonic development of the shell, 
have too wide an import to be employed in such a way. 
Horizon. Or^7iocm<s-Limestone ( = Arenig). 
Localities. Uitby, near Lake Siljan, and Kinnekulle Hill (Westro- 
gothia), Sweden ; Fossum, lliver Glommen, near Drdbak, Norway ; 
Reval (Esthonia), Eussia ; AYrietze, near Berlin. 
Well represented in the Collection, many very fine specimens 
having been presented by J. E. Lee, Esq., F.S.A., F.G.S. 
Endoceras vaginatum, Schlotheim, sp. 
1820. Orthoceratites vaginatus, Schlotheim, Petrefactenkiinde, p. 53. 
? 1844. Tlioracoceras vaginatum, Fischer, Bull. Soc. Imper. des Natu- 
ralistes de Moscou, tom. xvii. no. 3, p. 768, pi. xviii. f. 3. 
1860. Endoceras vaginatum^ Eichwald, Lethaea Eossica, vol. i. Seconde 
Section de I’ancienne Periode, p. 1243, pi. xlviii. fi: 1, a-e. ^ i 
1869. Orthoceras vaginatum, Karsten, Yerstein. des Uebergangsgebirges 
in den Gerollen der Herzogthiimer Schleswig und Holstein, p. 49, 
Tab. xvii. ff. 2, a, b, ? c. 
1881. Endoceras Zaddachi, Schroder, Schrift. der physikal.-okonom . 
Gesell. zu Konigsberg, Jahrg. xxii. Abth i. p. 93, Taf. iv. ff. 5, 
a, b, c, d. 
Ep. Char. Shell straight. Eate of increase about 1 in 11. Sec- 
tion slightly elliptical, the ratio of the diameters being as 13 : 12. 
Septa very numerous, about 8 being contained in a length of 1 inch, 
where the shell has a diameter of 1 inch 2 lines ; lessening very 
slightly in their distance apart as the shell augments in diameter. 
Siphuncle very large, occupying about half the longer diameter of 
^ Bull, American Mus. Nat. Hist. no. 1, New York, Dec, 23, 1881, p. 20. 
