TROCHOCERATID^. 
17 
the *Lethcea Svecica,' the septa being represented as much wider apart 
in the former illustrations than they are in the latter. The distance 
of the septa is an important point, because that is one of the cha- 
racters that separates Troclioceras lameUosum, His., from T. convolvans^ 
His., as may be seen by a comparison of the figure of the former 
species in the ‘ LethEea Svecica,' tab. viii., with that of the latter in 
the ‘ Anteckningar i Physik och Geoguosie,’ 1831, Heft v. tab. v. 
Feeling quite satisfied that the Diseoceras lamellomm of Angelin 
and Lindstrom is really the Troclioceras (“ Lituites^^) convolvans of 
Hisinger, I have placed it in the synonymy of the latter species. 
The specimen in the Collection which I have referred to the pre- 
sent species has remarkably close septa, which coincide with Hisin- 
ger's figure, but not with those of the ‘ Fragmenta Silnrica.’ Ho 
portion of the free whorl is seen in onr specimen, nor is the test 
preserved. 
Horizon. 0/'?7ioc*m(s-Limestone ( = Arenig). 
Locality. Sjurberg (Kopparberg ^), Sweden. 
Kepresented in the Collection by a single imperfect example pre- 
sented by Sir Ptoderick Murchison. 
Trochoceras convolvans % Hisinger, sp. 
1821. Liluitcc unpeifcctiores, Wahlenberg, Xova Acta Keg. Soc. Sclent. 
Upsalieusis, p. 84. 
1831. Lituites convolva?is^, Hisinger, Antecku. i Physik och Geoguosie, 
Femte Ilaftet, p. GO, tab. v. ff. 2, 2. 
1837. Lituites convolvans, Hisinger, Letlijea Svecica, p. 27, tab. viii. 
f. G. 
1880. Diseoceras convolvens, Angelin & Liudsti’om, Fragmenta Silnrica, 
p. 10, tab. ix. f. 12 (not tab. xvi. tf. 3 a-c). 
1880. Diseoceras lameUosum, Angelin Lindstrom, ibid. p. 10, tab. x. 
ff. 3-5, tab. XV. f. 30. 
[iVo^ 1820. Lithuites convolvans, Schlotlieim, Petrefactenkunde, p. 50. 
— 18G0. Lituites convolvens, Eicliwald, Lethma Rossica, vol. i. 
Seconde Section de Tancienne Periode, p. 1207.] 
Sji. Char. Shell discoid, with three and a half whorls, the last 
' The ancient province of Dalecarha or Dalarne. 
2 The following is Hisinger’s description of his species cmvolvans 
testa discoidea, spirali , anfractibus contiguis, teretibus, striatis, ultimo pro- 
longate; septis approximatis; siphone clorsali Diam. 3-4 uncias Par. 
[Parisian inches]. 
3 d’Orbigny (Prodr. de Paleont. Stratigr. vol. i. p. 27) renamed it Lituites 
Hisingerii, presumably to distinguish it from L. convolvans, Schlotlieim, whicli 
is, however, the L. lifnus, Breyn., and is therefore not synonymous with Hisin- 
ger’s species ; hence d’Orbigny ’s name is superfluous. 
PART II. C 
