86 Proceedings of the Royal Physical Society. 



and sharply-pointed spinelets. The tail is tapering in form, 

 consisting of amorphous-looking calcareous matter, but on 

 each side (assuming that the creature is crushed vertically) 

 is a conspicuous row of double spinelets (Figs. 6 and 7) 

 arranged exactly opposite each other. From a common 

 base arise two spinelets, which are placed close together, 

 and nearly parallel to each other ; one of them, the anterior, 

 being only half the length of the posterior one, which just 

 bahind the body may attain a length of yVth inch, though 

 towards the end of the tail they become smaller; both 

 spiaelets are slender, slightly curved, round in transverse 

 section, smooth externally, sharply pointed, and traversed 

 internally by a central tubular pulp cavity. No trace either 

 of internal skeleton, or of limbs, or fins of any sort, can be 

 seen. 



This strange organism is another of the problems of 

 Palaeozoic ichthyology, as it is scarcely possible to indicate 

 its systematic position with any degree of certainty. The 

 nature of its dermal armature would incline us to the belief 

 that it is a Selachian, though all other evidence to that 

 effect is wanting. — (From Ardross, collected by Mr W. T. 

 Kinnear, and now in the Edinburgh Museum.) 



Explanation of Plate Y. 



Fig. 1. CladodiLS unicusjndatiis, Traqnair, seen from the front; twice natural 

 size. Calciferous Sandstone Series, Rock and Spindle, near St 

 Andrews. 



Fig. 2. Another specimen of the same tooth, and belonging to the same 

 mouth, seen from the side. 



Fig. 3. Splienacanthus Fifensis, Traquair; natural size. Calciferous Sand- 

 stone Series, shore east of St Andrews. 



Fig. 4. Ccelacanthopsis curta, Traquair; natural size. From the shore at 

 Ardross. 



Fig. 5. Eucentrur us paradoxus, Traquair; natural size. From the shore at 

 Ardross. 



Figs. 6 and 7. Lateral spinelets of the tail region of Encentrurus paradoxus; 

 macfnified nine times linear. 



