RHADINICHTIIYS CANOBIENSIS. 135 



sharp denticulations of the hinder margin. Towards the back and belly (fig. 5) both 

 sets of markings tend to become confounded into one set of delicate, more or less 

 diagonal ridges and grooves, while towards the tail (fig. 4) these markings usually fade 

 away, a few punctures and longitudinal farrows being in most cases all that is to be seen 

 on the scales behind the dorsal and anal fins. In different individuals, however, very 

 considerable differences are to be found as regards the strength and prominence of the 

 scale-markings. In some the markings are very distinctly and sharply defined (fig. 2) 

 and the scales continue to be highly ornate up to the caudal body-prolongation, while in 

 others (fig. 3) even the scales on the front part of the body are comparatively smooth, 

 the oblique ridges becoming apparent only towards the posterior margin ; a reference to 

 the figures will, however, give a better idea of the variations in the general aspect of the 

 scale-sculpture than any amount of description. 



The pectoral fin is rather small, its length being hardly more than half that of the 

 head ; the princi{)al rays are unarticulated till towards their terminations. The ventrals 

 are small and delicate, and not well exhibited in any of the specimens. The dorsal fin 

 commences only very slightly in front of the anal, the two fins being thus placed nearly 

 opposite each other; they are very similar in shape and structure, being moderate in size, 

 acuminate, concavely cut out behind, and composed of delicate rays which dichotomise 

 towards their extremities, are distantly articulated, and have their brilliantly ganoid 

 joints marked usually by a single sharp longitudinal furrow, though even this is sometimes 

 wantino- save near the origin of the fin. Between the anal fin and the commencement 

 of the lower lobe of the caudal, is an interval fidly equal to the length of the i)ase of the 

 former. The caudal is also moderate in size, deeply bifurcated, and with a well- 

 developed body-prolongation along the upper lobe ; its rays partake of the same general 

 appearances as those of the dorsal and anal, though their articulations are a little closer, 

 and their surfaces usually quite smooth. Delicate fulcra are observable on the anterior 

 margins of all the fins. 



Geolojjical Position and Localities. — This is by far the most common fish in the 

 beds of Glencartholm, Eskdale, belonoino- to the Calciferous Sandstone Series. I have 

 also identified with it (under the name of R/i. dcgantdus) an imperfect specimen collected 

 by the Geological Survey of Scotland in the Calciferous Sandstone beds near GuUane in 

 East Lothian. 



The original types are in the Collection of the Geological Survey of Scotland, but the 

 specimen figured in this work (PI. XXX, fig. 1) belongs to the Royal Scottish 

 Museum. 



B. Vakiety eleffantul/is} Traquair. Plate XXX, figs. 7 — 11. 



Description. — Length 2^ to 2f inches, elegantly fusiform, general j)roportions as in 



1 In the explanation to PI. XXX Bhad'uiiclithys eleyantulus has been inadvertently entered as a 

 distinct species, instead of as a variety of Rh. canobiensis. 



