462 woodward: fossil fishes of the upper lias of whitby. ' 
recorded the species, without description, under the name of 
Gyrosteus mirabilis, still regarding it as the largest known fish; 
and he eventually considered it to be allied to his rather 
heterogeneous group of " Celacanthes." In 1858, Sir Philip 
Egerton published a memoir on the sturgeon-like fish, Chondrosteus 
acipenser aides, from the Lower Lias of Lyme Regis, and appended 
a footnote expressing the opinion that " the gigantic fossil fish 
of the Whitby Lias, named by Agassiz Gyrosteus mirabilis, 
belongs to the Sturionidse, and is nearly allied to Chondrosteus.'^ 
In 1876, Prof. J. F. Blake published a few notes on some of the 
specimens in the Yorkshire museums, but did not attempt an 
exhaustive treatment of the subject. His " large humerus (?) " 
is evidently the hyomandibular bone, while his problematical 
"radius or ulna" seems to be the ceratohyal. His "neural 
arch of vertebra" (op. cit., p. 257) or "spine" (ibid., p. 9., 
pi. ii., fig. 2) must be regarded as a caudal ridge-scute. 
Between the years 1889 and 1895 the present writer published 
further details of the osteology of Gyrosteus, confirming Egerton's 
suspicion of its close relationship to Chondrosteus ; and a com- 
plete summary of our knowledge of the fish up to the latter 
date is given in the British Museum Catalogue, pt. iii. 
According to Martin Simpson, who described one fragment 
of bone in the Whitb}^ Museum under the name of Sepia 
incomjyosita, the remains of Gyrosteus mirabilis occur in the 
compact bituminous shale immediately above the jet rock, 
which yields most of the fishes of the Whitby Lias. The large 
bones in collections are usually isolated and imperfect, frequently 
damaged by decaying pyrites ; and no complete head or any 
segment of the trunk has hitherto been excavated and preserved. 
The finest known slab of Gyrosteus mirabilis was purchased 
by the British Museum in 1861. It is represented of one- 
ninth the natural size in pi. Ixviii., fig. 1, and shows the 
scattered group of bones precisely as they were found, except 
that the separate fragment wdth the supraclavicle (s.cl.) 
originally formed a continuation of the angle marked f, and 
was removed for convenience of framing and preservation. To 
