888 DR RAMSAY EL TRAQUAIR ON FOSSIL FISHES. 



EXPLANATION OF THE PLATES. 



Plate I. 



All the specimens figured on this plate are from the " Ludlow " beds of Logan Water, and are 

 represented of the natural size, with the exception of figures 7 and 8. 



Fig. 1. Thelodus Scoticus, Traq., slightly deficient on the right side of the head, d, dorsal fin. From 

 a specimen collected and lent by Mr James Young, Lesmahagow. 



Fig. 2. Another specimen, showing the dorsal fin, also lent by Mr Young. 



Fig. 3. Another specimen, in Mr Young's collection, and showing the dorsal fin. 



Fig. 4. Another specimen, showing the contour of the head and lateral flaps. In the Collection of the 

 Geological Survey of Scotland. 



Fig. 5. Head showing the eye-spots. In the Collection of the Geological Survey of Scotland. 



Fig. 6. Another head showing the eye-spots, but not so distinctly as the previous specimen. 

 Geological Survey of Scotland. 



Fig. 7. Caudal scales, magnified. 



Fig. 8. Caudal scales in apposition, magnified. From a specimen lent by Mr Peter Macnair, 

 Glasgow. 



Plate II. 



All the specimens represented in this plate were collected by Mr Tait from the "Downtonian" horizon, 

 and are in the Collection of the Geological Survey of Scotland, except the original of fig. 4. 



Fig. 1. LanarMa liorrida, Traq., showing the eye-spots. From Birkenhead Burn. Natural size. From 

 Monks Water. 



Fig. 2, Head portion of a Lanarlcia-\\ke fish, with markings possibly indicative of branchial pouches. 



Fig. 3. Counterpart of the same specimen. 



Fig. 4. Lasanius problematicus, Traq., enlarged by one-half, the contour of the body, including the 

 caudal fin, being indicated by a carbonaceous film. From Birkenhead Burn. In the Royal Scottish 

 Museum, presented by the Geological Survey. 



Fig. 5. Another specimen, from Seggholm, twice natural size, showing the contour of the body, but 

 wanting the caudal fin. The oblique lines indicating the dorsal intermuscular septa are seen in the posterior 

 half of the specimen. Geological Survey of Scotland. 



Fig. 6. Another specimen, from Seggholm, twice natural size, showing well the heterocercal caudal fin, 

 while a few of the dorsal intermuscular septa are visible about the middle of the body. 



Fig. 7. Another specimen, from Monks Water, twice natural size, showing both dorsal and ventral 

 intermuscular septa. 



Fig. 8. Portion of the skin of a large specimen of Lasanius problematicus, from Birkenhead Burn 

 natural size, showing the post-cephalic rods, and behind and below these the dermal striations. 



Fig. 9. Impression of the outer surface of a head of Aleleaspis tessellata, Traq. From Birkenhead Burn. 



Fig. 10. Schematised vertical section of a scale of Ateleaspis tessellata, highly magnified. 



Plate III. 



The two specimens figured on this plate are from the "Downtonian" horizon, and are in the Collection 

 of the Geological Survey of Scotland. 



Fig. 1. Ateleaspis tessellata, Traq., a nearly perfect specimen, showing the contour of the head. From 

 The Mount, three miles south-east of Strathavon. Natural size. 



Fig. 2. Another specimen, wanting the head, but showing well the arrangement of the scales on the 

 body, and the contour of the dorsal and caudal fins. Natural size. From Birkenhead Burn. 



