66 FOSSIL FISHES OF THE ENGLISH CHALK. 



ring in the type specimen (fig. 1), those of the dorso-lateral and ventro-lateral 

 series interdigitating with those of the lateral line. All are very broad in propor- 

 tion to their length, and conspicuously ornamented. Each dorso-lateral scute 

 (fig. 1, d., and fig. la) Las the shorter arm directed dorsally, and this is truncated at 

 the end to meet its fellow of the opposite side in the median line of the back. The 

 sharp longitudinal ridge at the angulation of the scute ends in a sharp point in 

 front, while a small, backwardly-curved, uncinate spine is fixed upon its hinder 

 half (broken away in most cases, as in fig. la, but seen in side view towards the 

 hinder end of the fossil, fig. 1, d'). The descending or lateral arm of the scute 

 tapers to a point. Near to, and almost parallel with, the hinder border of the 

 scute, there is a strengthening ridge or angulation. The outer face is for the most 

 part ornamented with coarse tuberculations, which are sometimes arranged in rows 

 radiating forwards. Posteriorly these tubercles pass into low, reticulating ridges, 

 of which the principal direction is at right-angles to the hinder border. The scutes 

 of the lateral line (I.) closely resemble those of the dorso-lateral series in size, shape, 

 and ornamentation ; but both their arms are tapering, and they seem to lack the 

 uncinate spine on their angulation. The ventro-lateral scutes appear to be similar 

 to those of the dorso-lateral series and bear the uncinate spine ; but they are only 

 known by fragments (v.). 



Traces of the dorsal fin-rays (/.) are seen in the middle line of the back of the 

 type specimen between the paired series of scutes. 



Horizons and Localities. — -Probably zone of Terebratulina gracilis: Glynde, 

 Sussex. Specimen in the Enniskillen Collection (B. M. no. P. 3847) labelled 

 " Chalk, Kent," doubtless from a Turonian zone. 



2. Dercetis maximus, sp. no v. Plate XV, fig. 2. 



Type. — Fragmentary head and trunk from zone of Micraster coranguinum ; 

 British Museum. 



Specific ( 'haracters. — A comparatively large species, the head attaining a length 

 of at least 12 cm. External bones ornamented with very fine tuberculated ridges. 

 Dermal scutes of middle of* trunk broad, the three longitudinal series in contact and 

 interdigitating; their outer face ornamented with coarse tuberculations, variously 

 disposed in lines. Dorso-lateral scutes largest, broader than long; scutes of lateral 

 line about as long as broad, scarcely more than hall* as broad as the dorso-laterals ; 

 ventro-lateral scutes longer than broad, of medium size. 



Description of Specimen. — This species is known only by the type specimen, of 

 wliieli portions are represented in PI. XV, figs. 2, 2 a — c. The tip of the snout is 

 lost and only portions of the head are exposed from the left side. The remains of 

 the trunk are also very fragmentary. 



