LLANVIRN BEDS, ABEREIDDY, PEMBROK ESHIRE« 639 
in Barrande’s. As I consider that this character is due to an 
original structure and not to cleavage, it makes a sufficient specitic 
distinction between them. 
The geological horizon from which this new Conoceras was ob- 
tained is undoubtedly Llanvirn, because the fossils found with it 
are typical Llanvirn species. : 
Mr. Marr* correlates the Llanvirn beds with Ddly of Barrande, 
in Bohemia, and amongst the fossils enumerated from the latter he 
mentions Conoceras preposterum. In the list of fossils quoted by 
Mr. Marr + from the Orthoceras-limestone of Sweden, we find Bath- 
moceras Linnarsoni, and the upper part of this limestone he also 
correlates with the Llanvirn beds. 
CoNOCERAS LLANVIRNENSE. (Plate XXVIII.) 
Shell thin, cylindrical, marked with coarse corrugations corre- 
sponding to its lines of growth. Greatest width not less than 
2+ inches. Septa + to.3 inch apart; the sutures bent forward on 
each side of the siphuncle and meeting above it, forming a band of 
superposed chevrons. Siphuncle marginal. The specimen is much 
compressed, and the body-chamber is not seen. 
EXPLANATION OF PLATE XXVIII. 
Conoceras llanvirnense, Roberts, from the Lianvirn series, near Abereiddy 
Bay, Pembrokeshire: four fifths of the natural size. 
* Marr, Sedgwick Essay, p. 93. t Ibid. p. 121, 
