292 A.Smith Woodward — On Leedsia problematica. 



On comparing the head of Eiirycormns, as now described, with 

 that of the recent Amia, 1 there will be found to exist the most 

 remarkable similarity, not only in general features, but even in 

 points of detail. The membrane bones are all similar in form and 

 arrangement, and the majority differ little in relative proportions ; 

 the dentition is identical ; and even in so special and unusual a 

 feature as the direct articulation of the preoperculum with the 

 angular bone the two genera under comparison exactly agree. The 

 genus Evrycormns has already been placed in taxonomic works in 

 the same great group as the existing Amia ; and the new osteological 

 facts detailed above thus tend to confirm the accepted determination. 



II. — Note on the Gill-rakers of Leedsia problematica — a 



Gigantic Fish from the Oxford Clay. 



By A. Smith Woodwakd, F.G.S., F.Z.S. 



(PLATE X. Figs. 9, 10.) 



AT the last meeting of the British Association the writer briefly 

 described a remarkable series of bones of a large unknown 

 fish from the Oxford Clay of Peterborough, preserved in the col- 

 lection of Mr. Alfred N. Leeds, of Eyebury. The name of Leeds- 

 iclithys problematicus was proposed for the genus and species thus 

 indicated ; and the systematic position of the fish remained doubtful, 

 owing to the fragmentary character of its skeleton. 2 



No further discoveries of importance have hitherto been made, 

 but an opportunity is now afforded of publishing figures of two 

 imperfect gill-rakers (PI. X. Figs. 9, 10, 10a), which are perhaps 

 the most readily recognized and characteristic elements of the fish 

 in question. As shown in side-view (Figs. 9, 10), each gill-raker 

 is laterally compressed, slightly expanded at the basal extremity, 

 and rarely straight, but irregularly bent or contorted. The surface 

 is coarsely rugose, and one long border is rounded, while the other 

 is cleft by a longitudinal median furrow. The rounded border is 

 comparatively smooth, but the furrowed edge (Fig. 10a) is coarsely 

 serrated, a series of short oblique ridges terminating in points on 

 each side. 



It has been suggested that the generic name may be conveniently 

 shortened, that of Leedsia not being elsewhere occupied. The writer 

 hence proposes to refer to the fish in future as Leedsia problematica. 



EXPLANATION OF PLATE X. 



Fig. 1. Eurycormus grandis, A. S. "Woochv.; head, lateral aspect, two-thirds nat. 

 size. Kimmeridge Clay, Ely. [Woodwardian Museum, Cambridge.] 

 ag. angular, ao. antorbital. cl. clavicle, d. dentary. f. frontal. 

 ju. jugal. na. nasal, op. operculum, p. op. preoperculum. pa. 

 parietal, pr.f. prefrontal, pt.f. postfrontal. pt.o Y - z . postorbitals. 

 s.cl. supraclavicle. scler. sclerotic. so. suborbital, sq. squamosal. 

 st. supratemporal. x. doubtful bone. 

 „ 2. ■ hinder portion of cranium, superior aspect. 



1 R. ~W. Shufeldt, " The Osteology of Amia calva" Eep. U.S. Fish Commission, 

 1883, pp. 747-837, with plates. 

 3 Geol. Mag. [3] Yol. VI. (1889), pp. 451-453. 



