ORTHOCERATID-i:. 
63 
whole extent of the shell, crossing the annulations and their inter- 
spaces, so that the whole surface has the aj>pearance of a lattice- 
work. Between these riblets 1 or 2 much finer ones are occasionally 
developed. Lastly, fine and regularly disposed, horizontal, thread- 
like lines are placed in the intervals of the longitudinal riblets. The 
whole forms a striking and beautiful system of ornamentation, 
making the smallest fragments of the shell easily recognizable. 
RemarTcs. A brief description and a good figure of this species 
were given by Quenstedt (Joe. who adopted the name proposed 
for it by Barrande, to whom it had long been known in the environs 
of Prague. 
Horizon. Etage F, bande /2 (=Downtouian 
Localities. Konieprus, Prague, Bohemia. 
Well represented in the Collection. 
Orthoceras pulchmm, Barrande. 
1886. Orthoceras pulchrum, Barrande, Syst. Sil. de la Boheme, vol. ii. 
Texte iii. 1874 (janvier), p. 264, pi. ccxxii. ff. 19, 20, pi. cclxxvii., 
pi. ccccxlvi. ff. 7-11. 
Sp. Char. Shell perfectly straight. Section circular. Bate of 
increase very gradual, about 1 in 15. Body-chamber only imper- 
fectly known, but evidently very long, its length in a specimen 
measured being equal to 6| times the diameter of its base. Septa 
slowly and regularly increasing to a distance equivalent to ^ the 
diameter of the shell. Siphuncle central. Shell ornamented for the 
greater part of its length with transverse, sometimes a little oblique, 
annulations, varying in their distance apart in different individuals, 
but generally their distance is equal to J the diameter of the shell. 
These are traversed longitudinally by fine, rather closely placed 
riblets, about 3 of whicli are contained in the space of 1 line. 
Between these there are very fine and regular transverse lines, which 
can only be seen with the assistance of a lens. 
RemarJes. This species is closely allied to two others from the 
same horizon in Bohemia, viz. 0. pseudo-calainiteum, Barr., and 
0. pair onus., Barr. From the first of these it differs in having a 
much larger siphuncle, and in the closer approximation of the longi- 
tudinal riblets. From the second it is separated by its much slower 
rate of tapering, larger siphuncle, and by the character of its 
ornamentation. In 0. patronus the longitudinal riblets are much 
* Mr. J. E. Marr correlates Etage F with the Downtonian Series, or passage 
beds between the Silurian and Devonian Systems. “ The absence of Graptolites 
and the presence of fish bear out this view, as well as the abundance of large 
Pentameri and the presence of Goniatites.” (‘ Classification of the Cambrian 
and Silurian Rocks,’ p. 98.) 
