2 DE. A. SMITH WOODWARD ON A NEW SPECIMEN [Feb. I906, 



inferred that the larger ichthyodorniite named Myriacanthus para- 

 doxus by Agassiz, 1 belonged to the same fish as the larger dentition 

 named Prognatliodus Guentheri ; and in this determination I was 

 cod firmed -by the discovery of a very similar spine in association 

 with a Prognathodus-\ike dentition in the Lithographic Stone of 

 Bavaria. 2 The name Myriacanthus thus acquired a definite zoolo- 

 gical meaning, and no longer denoted a mere ichthyodorulite of 

 doubtful relationships. 



Until the present time, however, the spine named Myriacanthus 

 paradoxus has not been found in direct association with the 

 dentition described as Prognatliodus Guentheri. The expected 

 discovery has at ]ast been made, and as the new specimen displays 

 some additional features of interest, it seems worthy of special 

 description. The fossil in question (PL I, figs. 1-4) was lately 

 obtained by Mr. S. Curtis from the Lower Lias of Black Ven, and 

 has been acquired by the British Museum (Natural History), which 

 already possesses the specimens previously described. It shows the 

 dorsal fin-spine in direct connection with a mass of decayed cartilage, 

 dermal plates, and teeth ; and there can be no doubt that it 

 represents the crushed and partly-scattered remains of a single 

 individual. 



Much of the cartilage in the fossil is calcified in small polygonal 

 tesserae, which are especially large and conspicuous on the rostral 

 prolongation (r), and were originally mistaken by Egerton for 

 shagreen. Part of the ascending limb of the pectoral arch {pet) 

 is distinguishable among the confused remains. 



The dental plates are but slightly displaced, and are sufficiently 

 well preserved for identification. The right palatine {r.pa) is 

 exposed from the upper attached face, but its thin ascending 

 externo-lateral edge is crushed inwards. Allowance being made 

 for the small distortion, it exhibits the shape and proportions of 

 the corresponding plate already described in the so-called ' Pro- 

 gnatliodus GuentheriJ The left palatine (l.pa) is less satisfactorily 

 exposed from its lower or oral face, but exhibits the usual lack of 

 the tritor on an oblique patch in its anterior half. 3 One of the 

 vomerine plates (v) shows only the inner face by which it was 

 apposed to its fellow of the opposite side. The hinder part of the 

 lower border of the right mandibular dental plate is just visible (rnd\ 

 and the displaced presymphysial tooth (ps) is well shown from the 

 inner aspect. The latter tooth (PI. I, fig. 2) tapers rapidly to its 

 inserted end, while its inner face is flattened, marked only by feeble 

 transverse lines of growth, and bordered on each side by a rounded 

 raised rim. In cross-section, the outer part of the tooth shows 

 cancellated structure, and the tritor is confined to a thin inner layer. 



1 ' Eecherches sur les Poissons fossiles ' vol. iii (1837) p. 38 & pi. vi. 



2 K. A. vonZittel, ' Handbuch der Palaontologie ' vol. iii (1887) pp. 113-14 

 & fig. 126. See also J. Reiss, Palseontographica, vol. xxxiv (1887) p. 21, pi. ii, 

 figs. 9-11 & pi. iii, figs. 1-10. 



3 See 'Catalogue of the Fossil Fishes in the British Museum' pt. ii (1891) 

 pi. ii, fig. 1. 



