244 



NATURAL SCIENCE. 



Oct., 



the skeleton, taken from the newly-issued part of the Proc. Roy. Phys. 

 Soc. Edinhiirgh (vol. xii,, pp. 312-320, pi. ix.), is reproduced below for 

 comparison with those previously attempted. It now appears that 

 the animal had a median opening or ring, surrounded with feelers, at 

 the front of the head ; this being presumably comparable with the 

 nose of a modern lamprey. It is also evident that the fin-supports at 

 the end of the tail are longer than previously suspected ; and those at 



Pala-ospojidylus ^uiini ; new restoration by Dr. R. H. Traquair, somewhat 

 enlarged, d.c, dorsal cirri; I.e., lateral cirri ; «., nasal opening ;/.«., periotic 

 region of skull ; t.p., anterior part of skull, with indents marked a., b., and c. ; 

 v.c, ventral cirri ; x., problematical (? branchial) plates. 



least of the dorsal aspect are proved to bifurcate towards the top, 

 exactly as in a lamprey. That PalcBOspondylus is a primaeval Marsipo- 

 branch is thus suggested still more forcibly than ever, and the next 

 important step is to discover the links between this little organism 

 and some of its yet more remarkable contemporaries, Ptevaspis and 

 Cephalaspis. 



The Armoured Fore-runners of the Chordata. 



Remarkable additions to our knowledge of the last-named 

 animals, now commonly assigned to a subclass termed Ostracodermi 

 or Ostracophori, have lately been made by Dr. J. V. Rohon and Dr. 

 Friedrich Schmidt in the publications of the St. Petersburg Imperial 

 Academy of Sciences. The descriptions, both of the form of the 

 sh\&\^s oiTremataspis, Auchenaspis (Thyestes), and fragments of allied 

 genera, are supplemented by a detailed, well-illustrated account of 



