Manchester Memoirs, Vol. Ix. (1916), No. %. 13 



Rhizodopsis sauroides is of interest for many reasons. 

 In his original paper Williamson described it as " an extinct 

 salmon " on superficial resemblance of squamation. But 

 even in his earliest paper he gave an account of a some- 

 what distorted fish showing all the fins. This specimen 

 was the first nearly complete fish to be found in the 

 Lancashire coal measures or indeed we believe in the coal 

 measures of England. It is now in the Manchester 

 Museum and has served us for a study of the median fins. 

 Our knowledge of the fish however really depends on a 

 classical description which Dr. Traquair gave in 1881, the 

 first thorough study of the cranial osteology of a Crossop- 

 terygian fish ever published in England. The materials 

 which we have used consist of eight specimens from the 

 Knowles Ironstone of Fenton, Staffordshire, and numerous 

 specimens in shale, two of which, one being Williamson's 

 original, are important for the study of the median fins. 

 An entirely independent restoration of the head made 

 from this material agrees with that given so long ago by 

 Dr. Traquair in all important features but differs slightly 

 in the proportions of certain bones, and in the general 

 shape. In addition we have observed a small process 

 rising from the anterior end of the maxilla, whose 

 anterior border forms a rounded margin which can only 

 be that of an external nostril. As this process is not 

 present in all specimens it is in all probability really a 

 separate bone. In addition we have observed the presence 

 of a series of well interlocked sclerotic plates in the eye- 

 ball bearing a very considerable resemblance to those 

 which are so familiar in Ichthyosaurus. We have observed 

 considerable difference in proportion of bones in fish of 

 different sizes. 



One remarkable specimen in the Knowles Ironstone 

 shows a good deal of the cartilaginous portions of the 



