BARRANDE SILURIAN CEPHALOPODS. 



15 



Sections. 



Categories. 



W 



II. 



^^ 



o 



Long-coned 

 Orthocera- 

 tites {con- 

 tinued). 



Mixed orna- 

 mentation. 



Transverse or- 

 naments pre- 

 dominating. 



Smooth shell, 

 or slightly 

 striated across, 



Lines and striae upon the whole of the 

 length, Avith rings towards the point or 

 middle region. 0. Bronni, Barr., 0. 

 electrum, Barr., 0. Nejjtuni, Barr. 



Lines and stria} upon the whole of the 

 length, with rings over the whole surface. 

 0. patronus, Barr., 0. -pidchrum, Barr., 

 O.'pseudocalamiteum^'B-diYr., 0. solitariicm, 

 Barr. 



Simple longitudinal lines, crossed by trans- 

 verse lines of about equal intensity. 0. 

 set'icatum, Barr., 0. loricatum, Barr., 0. 

 mimits, Barr., 0. contextum, Barr. 



Yariable species in which sometimes the 

 longitudinal and sometimes the trans- 

 verse ornamentation predominates. 0. 

 araneosum, Barr., 0. mctima, Barr., 0. 

 mutabile, Barr. 



Rings vipon some part of the surface, ac- 

 companied only by rectilinear or sinuous 

 transverse stria;. 0. dulcp., Barr., 0. an- 

 nul atiim, Sow., 0. Agassizi, Barr,, 0, no- 

 biJe, Barr., 0. lunaticum, Barr., 0. Nerei- 

 dum, Barr., 0, rigescens, Barr. 



Transverse bands upon the surface, with 

 superficial undulations, flattened rings, 

 and deep grooves. 0. pedum, Barr,, 0. 

 rivale, Barr., 0. fasciolatum, Barr., 0. 

 a-phragma, Barr., 0. zonaium, Barr. 



Transverse striae, which are distinguished 

 by transverse imbrication. 0. jpleuroto- 

 mum,lSeirr., 0. placidum, Barr., O.Janus, 

 Barr., 0. Giebeli, Barr. 



Transverse stride, showing direct imbrica- 

 tion. 0. Simois, Barr., 0. Lychas, Barr., 

 0. timidum, Barr., 0. asparagus, Barr. 



Transverse strise, without sensible imbrica- 

 tion. 0. capax, Barr,, 0. Minos, Barr., 

 0. Hosrnesi, Barr., 0. valens, Barr. 



Species with a lamellose shell, which are 

 not included, by reason of their more de- 

 cided characters, in other groups. 0. 

 sevcrum, Barr., 0. squamatidum, Barr., 

 0. vulpes, Barr., 0. Bichteri, Barr. 



Well-mai-ked transverse striae, without pro- 

 nounced imbrication, but with very fine 

 longitudinal striai in the spaces between 

 the transverse striae. 0. senile, Barr., 

 0. passer, Barr., 0. Eichwaldi, Barr,, 0. 

 Halli, Barr. 



Little perforations of the shell, which co- 

 exist with both transverse and longitudi- 

 nal strise. 0. i)orites, Barr., 0. venustu- 

 lum, Barr., 0. Saturni, Barr., 0. subtile, 

 Barr. 



Smooth shell, with occasional traces of 

 transverse striae. 0. aperiens, Barr., 0. 

 Tritonum, Barr., 0. Avion, Barr., 0. de- 

 cipiens, Barr. 



