368 TEILOBITES. 



The genus Paradoxides was established by Brongniart in 1822 (Crust, foss. p. 30); and the fossil 

 described by Linne under the name of Entomolithus paradoxes, as figured and described by Wahlenberg 

 (Act. Soc. Upsal. 1821, pa. 31, pi. 1, f. 16), was made the type of the genus under the name Paradoxides 

 tessini. Under the same genus were included P. spinulosus, P. scarabceoides and P. laciniatus; species 

 described by Wahlenberg, reproducing the figures of that author, and giving an additional illustration of 

 P. spinulosus. 



In 1826, Dalman, admitting the genus Paradoxides of Brongniart, nevertheless proposed the name 

 Olenus to include the four first named species; placing P. tessini and P. spinulosus in the first section, 

 and the others in the second section of the new genus, proposing the generic name of Lichas for the 

 P. laciniatus of Brongniart. Subsequently the three species P. spinulosus, P. gibbosus and P. scarabceoides 

 have been regarded as distinct from Paradoxides, and made the foundation of the genus Olenus ; while the 

 latter of these has more recently been placed under the genus Peltura. 



In Paradoxides, as now established, we have species with broad lunate cephalic shields, with the glabella 

 wider in front: the body or thorax has from sixteen to twenty articulations; the pygidium is narrow, with 

 two to three and even five and eight segments, while the lateral lobes are little developed. 



In Olenus, the cephalic shield is comparatively broader and shorter, the glabella narrowing (or not 

 broader) anteriorly: the number of thoracic segments is from fourteen to sixteen; the caudal shield is 

 broader than long and semicircular, the lateral lobes being more developed than in Paradoxides, and both 

 marked by transverse rings or ridges. 



M. Barrande makes the following comparisons between Paradoxides and Olenus: 



" In establishing the family for which we have given Paradoxides as the type, we have indicated the 

 characters common to the genera which constitute it. Notwithstanding their affinities, it is easy to 

 recognize at a glance that the Paradoxides are distinguished by the larger number of segments, the form 

 of ribs, the hypostoma, the great prolongation of the cephalic limb, the very elongated eyes, and the 

 general appearance. The only type where it is difficult to establish a strong line of demarkation, is 

 Olenus; particularly when we consider P. spinulosus, which approaches nearest to Paradoxides, and 

 which Burmeister has classed with them. Not having at our disposal the materials necessary to show 

 fully the distinction between these two genera, we will confine our remarks to: 1, That in Olenus, the 

 glabella has a form constantly narrowing towards the front, and which contrasts with those of the 

 Paradoxides; 2, the lateral furrows of Olenus are very much inclined, and rarely unite in pairs on the axis, 

 while in Paradoxides they are almost horizontal, and the two last pairs generally form two parallel branches 

 traversing the glabella; 3, the number of thoracic segments in the first genus appears not to exceed 

 fifteen or sixteen, which is the least number observed in the second; 4, the pygidium of Olenus usually 

 differs from that of Paradoxides by a greater relative development of the lateral lobes. We hope that 

 the Swedish savants will be able to define the limits between the two genera. The discovery of the 

 hypostoma of Olenus would contribute much to attain this end." * 



In comparing our own species with Olenus, we find some differences in the form of the cephalic shield 

 but more particularly in the form of the glabella; which, however, from imperfection in the specimens, 

 does not admit of minute comparisons. Our specimens have no more than thirteen or fourteen segments 

 of the thorax (and the one referred to Peltura has eleven), instead of fifteen or sixteen, and the direction 

 of the lateral furrow is different. The greater development and extension of the third segment of the 

 thorax is a remarkably distinctive character, and the same feature is shown in the posterior segments of 

 one species. The form and development of the pygidium also differs from that of Olenus, in the lesser 

 lateral expansion, and absence of segments on the lateral lobes. 



When we compare with Paradoxides, we find the cephalic shield proportionally broader and shorter, 

 while there is no expansion of the glabella towards the front; nor do the transverse furrows extend entirely 

 across this part, except at its base. This feature and the facial suture, though indistinct, correspond more 

 nearly with Olenus. 



* Barrande, Systeme Siturim ducentre, dc la Bohime, Vol. I, p. 867. 



