CYETOCERATID^. 
289 
b. Endogastric, 
LoXGICOIfES. 
Cyrtoceras (Meloceras) neutrum, Barrande, sp. 
1867. Cyrtoceras neutrum^ Barrande, Syst. Sil. de la Bobeme, vol. ii. 
pt. i. p. 679, pi. clxv. fF. 1-7, pi. cc. tf. 5-8. 
Bp. Char. Examples of this species are always more or less strongly 
arcuate, and the shell would form at least half a whorl if complete. 
The transverse section is oval ; the slightly smaller of the two ex- 
tremities corresponding with the concave border of the shell. The 
ratio of the two diameters of the oval is as 5 : 4, increasing to about 
4 : 3 in some individuals. The rate of increase is 1 in 2 ; but 
this varies a little in different examples, the dilatation being more 
rapid in the apical portion of the shell, as in other species of Melo- 
ceras. The body-chamber is relatively short, occupying about | of 
the total length of the shell. The aperture shows a very distinct 
sinus on the concave side, and a verj* shallow one appears also on 
the convex border. The distance of the septa from each other is 
equal to about of the ventro-dorsal diameter of the shell. The 
siphuncle is placed close to the concave border ; it is slightly inflated 
between the septa, so that its elements are nummuloidal in character. 
The test is ornamented with striae of growth somewhat irregularly 
spaced and of unequal strength. 
Remarhs. The nearest ally of the present species is M. Mnrcliisoni., 
Barr., sp. (pis. clx., clxv., &c.), but the latter has a much more 
rapid rate of tapering, and the body-chamber is considerably larger 
in proportion to the entire shell. 
Barrande compares the present species with M. intermedium^ 
M‘Coy, sp. ( = J/. arcuatum, J. de C. Sow., sp.), to which he finds 
that it bears a strong resemblance. I shall have occasion to refer 
to this subject again when dealing with the latter species h 
Horizon. Etage E ( = Salopian). 
Localities. Lochkow, Dlauha Hora, Bohemia. 
Eepresented in the Collection by three examples. 
Brevicojstes. 
Cyrtoceras (Meloceras) aduncum, Barrande, sp. 
1848. Cyrtoceras aduncum, Barrande, Haidinger, Berichte fiber die 
Mittheil. von Freund, der Naturwiss. in Wien, p. 209. 
See infra, p. 303, under M. M‘Coyi. 
V 
