SYNECHODUS. 217 



in direct association with the skeleton, but it is almost certain that they are 

 included among those usually named iSjihuix iiuijor (see p. 21 (i). No ribl)ed fin- 

 spines have been found in the Chalk ; the fragments in the Mantell Collection 

 described as Hi/hodits snhatus "from the Chalk of Lewes" (L. Agassiz, Poiss. 

 Foss., vol. iii, 1837, p. 44, pi. x h, figs. 15, 16) being truly Wealden fossils. 



1. Synechodus dubrisiensis (Mackie). Plate XLV, figs. 6, 7; Plate XLVI, 



figs. 1, 2. 



1863. Hyhodus dnhrisiensis, S. J. Mackie, Geologist, vol. vi, p. 241, pi. xiii. 

 1886. Hyhodus (0 dvhrisiensis, A. S. Woodward, Proc. Zool. Soc, p. 218, pi. xx. 



1888. Synechodus dubrisiensis, A. S. Woodward, Proc. Geol. Assoc, vol. x, j). 288; aud Geol. Mag., 

 [3] vol. V, p. 496, woodcut. 



1889. Synechodus dubrisiensis, A. S. Woodward, Catal. Fofs. Fishes B. M., pt. i, p. 327, text-fig. 12, 

 l^l. xi, figs. 17 — 20, pi. xii, fig. 6. 



1894. Synechodus dubrisiensis, A. S. Woodward, Proc. Geol. Assoc, vol. xiii, p. 193, text-fig. 1. 



Tyjje. — Jaws with a few teeth from the zone of Holasfer snhglohosus ; British 

 Museum. 



Specific Characters. — The type species, with jaws attaining a length of about 

 8 cm. Tlie continuous base of the crown in all the teeth marked by fine 

 reticulating Avrinkles, and at least tlie lower portion of the coronal cusps vertically 

 striated. Supposed upper anterior teeth robust, the coronal surface prominently 

 striated almost to the acute apex, and the comparatively small lateral denticles 

 three or four in number; base-line of crown gently arched. Supposed lower teeth 

 of the anterior pair minute, the main cusp slender, with two denticles on the 

 symphj^sial side, one denticle on the other ; following teeth with well-developed 

 and well-separated acute lateral denticles. Hinder teeth slender and much 

 extended, with both main cusp and lateral denticles reduced to smooth beads. 



Description of Specimens. — The jaws of the type (PI. XLV, fig. 6) are smaller 

 than those of most specimens, evidently belonging to a yotmg individual. With 

 these and each of the other known jaws there are a few scattered teeth ; and one 

 fossil in the Willett Collection (PI. XLVI, fig. 1) exhibits the wdiole of the 

 dentition presumably of the mandible. In one specimen (PI. XLVI, fig. 2) remains 

 of the jaws are directly associated with part of the skull, vertebral column, and 

 pectoral arch. 



In all cases the cartilages are calcified only in a thin superficial layer, but this 

 is sufficiently compact for good preservation. The shape of the jaws is thus 

 distinguishable in several specimens. The pterygo-quadrate or upper jaw (PI. 

 XLV, figs, 6, 7, ptq.) deepens upwards at the end of its anterior third into an 

 acute pterygo-trabecular process {p.) ; while at the end of its middle third it rises 

 into a much higher otic process {ot.), which in one specimen (fig. 7) clearly bears a 



28 



