320 Proceedings of the Royal Physical Society. 
the hope that still further patient search in the quarry on 
Achanarras Hill will be rewarded by the discovery of material 
whereby our knowledge of the structure of Palwospondylus 
will be rendered still more complete. 
LITERATURE OF PALAOSPONDYLUS. 
1. Traquatr, R. H., On the Fossils found at Achanarras Quarry, 
Caithness, Ann. and Mag. Nat. Hist. (6), vol. vi., 1890, 
p. 485. 
Woopwarp, A. Smitu, Catalogue of the Fossil Fishes in the 
British Museum, pt. i1., 1891, p. 553. Reference to the 
above. 
3. Howes, G. B., On the Affinities, Inter-Relationships, and 
Systematic Position of the Marsipobranchii, Z’rans. Biol. 
Soc. Liverpool, vol. vi. (1891). 
4, Woopwarp, A. SmitH, The Forerunners of the Backboned 
Animals, Vatural Science, October 1892, pp. 597-599, fig. 1. 
5. Traquarr, R. H., A further Description of Paleospondylus 
Gunni, Proc. Roy. Phys. Soc. Edin., vol. xii., pt. i, 
1893, pp. 87-94, Pl. I. Reviewed by Mr Smith Woodward 
in Vat. Science, August 1893, p. 128, and in Geol. Mag. (3), 
vol. x., p. 471. 
6. Dawson, J. W., Salient Points in the Science of the Earth, 
London, 1893, pp. 285, 286. With a figure. 
i) 
EXPLANATION OF PLATE IX. 
The lettering is uniform throughout all the figures. ¢.p., anterior or 
trabeculo-palatine part of the cranium; p.a., posterior or parachordal part; 
a., lobe divided off from the anterior part; b., anterior depression or fenestra; 
c., posterior depression or fenestra; ”., nasal ring; v.c., cirri of the ventral 
margin of the ring; 7.c., long lateral cirri; d.c., cirri of the dorsal margin; 
v., vertebral centra; x., post-occipital plates. 
Fig. 1. Head of Palaospondylus Gunni, seen from the ventral aspect, and 
showing the presumed nasal ring with its cirri. The rest of the cranium is 
eroded. Magnified five diameters. 
Fig. 2. Another head; the two inner cirri of the ventral part of the ring 
lost; the rest of the cranium eroded. Magnified six diameters. The entire 
specimen represented of the natural size in Fig. 7. 
Fig. 3. Another head still more eroded, but the position of the nasal 
opening indicated by the remains of the cirri around it. Magnified six 
diameters. 
