Arthrodires 



In a recent paper Dr. Otto Jaekel unites 

 Arthrodires and Ostracophores under the name 

 Placodermi. He regards Pteraspis as a larval 

 type, Asterolepis as one more specialized. In 

 Coccosteus he claims to find a pelvic girdle as 

 well as a more segmented skeleton. He regards 

 all of these as true fishes, the Coccosteida asi 

 ancestral, related on the one hand to the Cross- 

 opterygians, and on the other to the Stegocephali 

 and other ancestral Amphibians. 



Suborder Cycliae. We may append to the Arthro- 

 dira as a possible suborder the group called Cyclia 

 by Dr. Gill, based on a single imperfectly known 

 species. Few organisms discovered in recent times 

 have excited as much interest as this minute fish- 

 like creature, called Palaospondylus gunni, dis- 

 covered in 1890 by Dr. R. H. Traquair in the 

 flagstones of Caithness in Scotland. Many speci- 

 mens have been obtained, none more than an inch 

 and a half long. Its structure and systematic 

 position have been discussed by Dr. R. H. Traquair, 

 by Woodward, Gill, Gegenbaur, and recently by 

 Dean, from whose valuable memoir on " The Devonian 

 Lamprey " we make several quotations. 



Palaeospondylus. According to Dr. Traquair : " The 

 Pal&ospondylus gunni is a very small organism, usually 

 under one inch in length, though exceptionally 

 large specimens occasionally measure one inch 

 and a half. ... It has a head and vertebral 

 column, but no trace of jaws or limbs; 

 and, stiange to say, all the specimens 

 are seen only from the ventral aspect, 

 as is shown by the relation of the 

 neural arches to the vertebral 

 centra. 



' ' The head is in most cases <^^^PP 

 much eroded. ... It is di- 

 vided hv a notrh into Fl0 ' . 369< ^ Palrf0 *pondylus gunni Tra- 

 quair. Devonian. (After Traquair and 



two parts. . . . The anterior Dean.) 



