64 WEALDEN AND PURBECK FOSSIL FISHES. 



pari of their extent solely by the thickened anterior rim. The ridge-scales, which 

 arc arranged in a regular close scries, are much thickened, and each bears a row of 

 three large, hollow, smooth denticles increasing in size backwards, sometimes with 

 an additional one or two minute denticles in front. The massive smooth ridge- 

 scales of the ventral bonier exhibit, wide facettcs for overlap by the lowesl 

 flank-scales (PI. XIV, figs. 1 b, 2) ; while each of those of the dorsal border is 

 produced downwards into a triangular lateral wing, which is more or less 

 ornamented by reticulations like the other scales. The flank-scales are complete 

 only in the lower part of the abdominal region, diminishing in number and vertical 

 extent backwards. As shown by a specimen from Ridgeway, in the Dorset County 

 Museum, there are five of these scales in at least one anterior transverse series, 

 four scales in several following series, then three scales, and finally only two 

 complete scales in at least one series adjacent to the origin of the anal fin. All 

 these scales (PI. XV, fig. 3) are much deeper than wide, increasing in depth 

 upwards, and the uppermost scale ends in an attenuated apex. The line of union 

 between each scale and the next above is very oblique, and the posterior border is 

 gently convex. The outer surface is ornamented with reticulations which tend to 

 radiate from the middle of the smooth anterior margin. This marsdn has a wide 

 thickening on the inner face, which forms the usual deep peg-and-socket 

 articulation (PI. XV, figs. 4, 5). At the position of the pelvic fins, which are 

 inserted in a triangular hollow on the flank just above the ventral border, the 

 lowest scales of two transverse series diverge to allow the intercalation of a deep 

 triangular scale, and one of the ridge-scales is extended to bear a second, facette 

 for the overlap of this additional scale (as shown in PI. XIV, fig. 2, dr.). The 

 lateral line passes through a perforation in the degenerate riblet of at least the 

 two anterior series of scales ; and all the riblets immediately below the dorsal 

 ridge-scales are slightly widened and pierced along the course of the upper 

 lateral line. A single smooth, nearly rhombic scale is also sometimes seen at the 

 base of the caudal fin, perhaps the last remnant of the squamation of an upper 

 caudal lobe. 



The principal characters of the species, as now described, are shown in the 

 restoration of the fish, Text-fig. 23, p. 60. 



Horizon and Localities. — Middle Purbeck Beds: Swanage and neighbourhood 

 of Weymouth, Dorset. 



Genus CCELODUS, Heckel. 



Coelodus, J. J. Heckel, Sitzungsb. k. Akad. Wiss. Wieii, math.-naturw. CI., vol. xii, 1854, p. t55. 

 Glossodus, 0. G-. Costa (non McCoy, 1848), Atti Accad. Poiitan., vol. vii, L853, p. 26. 

 Coemodus, H. E. Sauvage, Bull. Soc. Sci. Nat. Yomie, vol. xxxiii, pt. ii, lsi~!». p. 18 



