i20 /Scientijic Intelligence. 



Oh>))dl>iS is not homoloo-()us with the pygidinm of most trilobites 

 but tliat it is a spocialized post-thoracic one at least 11 segments 

 anterior to the pygidium in the most primitive genus of the 

 family, namely Nevadia. In other words, when the specialized 

 OIowUhs is compared with the more primitive Nevadia it is seen 

 that the former has not only lost its pygidium but at least 13 

 other i)ost-thoracic segments, and that the telson of OleneUns is 

 probably homologous with either one of the 15th to 17th post- 

 cephalic segments of Nevadia, back of which in this genus there 

 are still 1 1 other segments and the true j)ygidium. How these 

 post-thoracic segments are lost and how the telson is developed 

 out of a spine in the diflferent genera is fully described and illus- 

 trated by the author. This unmistakable evolution probably also 

 indicates that the telson of lAmulus is not homologous with the 

 pygidium of trilobites, but that it is as well a specialized thoracic 

 segment, and one equivalent to a thoracic segment considerably 

 in advance of the pygidium of its trilobite ancestors. 



It is now also made more apparent that the head of the Meso- 

 nacidje is highly specialized in that the compound eyes have 

 traveled from the ventral to the dorsal side in the earliest onto- 

 genetic stages, for they have the relative position of maturity so 

 eai-ly as in the para!protaspis stage. Furthei', the free cheeks are 

 firmly united with the glabella, do not separate along the facial 

 suture as in most trilobites, and in this again recall the similar 

 condition in Limidns. Genera like OleneUns are, therefore, 

 highly specialized trilobites and are decidedly removed from the 

 primitive types of which Alops and Gonocoryphe are examples. 



For the first time the eye cavities in the Mesonacidae have been 

 discovered and are here illustrated. They are very much like 

 those in Limulus. 



As is well known, the author is assembling Cambrian fossils 

 from all parts of the world and in the work here reviewed we get 

 a glimpse of the grandeur of the Smithsonian collections. When 

 his studies are completed we will not only have a detailed knowl- 

 edge of the oldest fossil faunas of the world but as well a firm 

 base upon which to build our phylogeniesof the trilobites, phyllo- 

 pods and brachiopods. c. s. 



4. Die Seller ophonhalke von Oberlcrain und ihre Brachio- 

 podenfauna ; by F. Kossmat and C. Dienee, Jahrb. k. k. geolog. 

 Reichs., 1910, pp. 277-310, pis. 14-15.— The Bellerophon lime- 

 stone and dolomite of the eastern Alpine region are at the top of 

 the Paleozoic section and in close connection with the Triassic. 

 They are underlain by red and white sandstone and conglomerate 

 that in turn rest upon the black slates of the Carboniferous. These 

 littoral deposits evidently represent a new sea invasion and are 

 correlated by Kossraat with the Grodener and Verrucano, the 

 normal aspect of the southern Alpine Permian sandstone. Above 

 the Bellerophon horizon there repose disconformably the sandy- 

 micaceous Werfener beds of the Triassic characterized by 

 Pseudomonotis aurita, P. ovata and P. venetiana. 



