PALsEOSPONDYLUS GUNNI FROM CAITHNESS FLAGSTONES 95 



alcohol, it must be admitted that the difficulty in the \vay of 

 getting any evidences of fossil Marsipobranchs is extreme. 



The minute tooth-like bodies known as conodonts, which 

 have been found in the greatest variety of form in Silurian and 

 Carboniferous rocks both in Europe andAmerica,have by many 

 been supposed to have possibly belonged to Marsipobranch 

 fishes, while others have been inclined to refer them rather 

 to Mollusca or to Annelides. In an elaborate paper pub- 

 lished in 1886, Professor von Zittel and Dr. Rohon, 1 after 

 careful microscopic study of the bodies in question, totally 

 discard the Marsipobranch theory, and record their belief that 

 the entire series of conodonts must have belonged to the 

 oral apparatus of Worms. 



In 1890 I briefly noticed (i) a small organism from the 

 Old Red Sandstone of Achanarras, Caithness, which I named 

 Palceospondylns Gunni after its discoverers Dr. Marcus Gunn 

 and Mr. Alexander Gunn, and whose head, apparently formed 

 of calcified cartilage, seemed to me to suggest a Marsipo- 

 branch affinity ; but as it also possessed a segmented 

 vertebral column, I admitted that a Myxinoid with ossified 

 skeleton including differentiated vertebral centra was rather 

 a startling idea. The idea was, however, favourably received 

 by Professor Howes (3) and Mr. Smith Woodward (4), and last 

 year I was able to follow it up by publishing a more detailed 

 account (5) of the structure of this remarkable fossil from 

 fresh material. In August last (1893) I obtained still more 

 perfect specimens from Achanarras, a description of which 

 (7) I read before the Royal Physical Society of Edinburgh 

 in the following December. 



As this little organism is of great zoological interest, and 

 has as yet been found nowhere else than in one locality in 

 the north of Scotland, a brief resume of its structure may be 

 considered a suitable contribution to the " Annals of Scottish 

 Natural History." 



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: its 

 appearance, natural size, is shown in Plate III. Fig. 7. It has 



1 " Ueber Conodonten." Sitzitngsb. der bayer. Acad. dcr H T issenschaften 1886. 

 Mathem.-phys. Classe, pp. 108-136. 



