Description of Paleeospondylus Gunni. 87 
VIIL A further Description of Paleospondylus Gunni, 
Traquair. By R. H. Traquatr, Esq., M.D., LLD., 
F.R.S. [Plate I.] 
(Read 18th January 1893.) 
Paleospondylus Gunni is the name which I gave, a little 
more than two years ago,’ to a strange little vertebrate 
organism from the Old Red Sandstone of Achanarras, Caith- 
ness, the original discovery of which we owe to Dr Marcus 
Gunn and his cousin, Mr Alexander Gunn. It is a very 
small creature, usually under an inch in length, showing a 
head and vertebral column, but neither jaws nor limbs, 
and, when first discovered, was supposed by some who saw 
it to be possibly a young condition of Coccosteus. Concerning 
its affinities, I expressed myself as follows :— 
“Tt is very difficult to give an opinion on the affinities of 
this strange little organism, except that it is a vertebrate, 
and probably a fish. It is certainly not a Placoderm, its 
resemblance to a supposed ‘baby Coccosteus’ being entirely 
deceptive. The appearance of the head does remind us in a 
strange way of the primitive skull of Myzine, a resemblance 
which is rendered still more suggestive by the apparent com- 
plete absence of lower jaw or limb-girdles. But a Myxinoid 
with ossified skeleton, including differentiated vertebral centra, 
is, it must be owned, a rather startling idea!” 
Undoubtedly this is a startling idea—but the Marsipo- 
branch theory of its affinities has found favour with at least 
two morphologists who have had the opportunity of examin- 
ing the original as well as other specimens. Professor G. B. 
Howes,? of the Royal College of Science, writes: “The 
palzontological history of the Marsipobranchii, until lately 
estimated upon the supposition that the conodonts, some of 
which have. been claimed as annelide jaws, are Marsipo- 
branch teeth, has recently undergone a revolution, in 
Traquair’s description of a very remarkable fossil from the 
Old Red Sandstone at Caithness, which he has named 
Paleospondylus Gunni, after its discoverer. . . . I fully 
acquiesce in his having provisionally referred the creature 
1 Ann. and Mag. Nat. Hist. (6), vol. vi., 1890, p. 485, fig. 4. 
* Trans. Biol. Soc. Liverpool, vol. vi., pp. 143, 144. 
