RHADINICHTHYS MACCONOCHII. 141 



posteriorly. Towards the tail (fig. 10) the vertical furrows become imperceptible or 

 reduced to a single one. ]3elow the lateral line the scale-ornament is for the most part 

 less marked, though similar in character, but towards the tail-pedicle little or no 

 difference is seen above and below. 



The pectoral fin is scarcely more than half the length of the head ; its principal rays 

 are unarticulated till towards their terminations. The ventral (see fig. 7) is very small, 

 and situated a little behind the middle point between the pectorals and the anal. The 

 dorsal is placed far back, being nearly exactly opposite the anal; both of these fins are 

 similar in appearance, being moderate in size, triangular, acuminate, and slightly cut 

 out behind ; their rays are of inedium coarseness, smooth, dichotomising towards their 

 extremities, and distantly articulated. The caudal is well developed, heterocercal, 

 deeply cleft, the rays similar in appearance to those of the dorsal and anal ; in the lower 

 lobe dichotomising towards their extremities, in the upper towards the middle. Well- 

 developed fulcra are seen along the fin-margins. 



Observations. — The position of the above-described species in the genus BhadlnicUhys 

 is indicated by the structure of the pectoral fin, by the shape of the scales, and the 

 nature of their sculpture, even although the scales are not denticulated posteriorly, and 

 although the dorsal fin is placed still further back than is usual in Mhadinichihys, 

 its position being hardly, if at all, in advance of the anal. These two last-mentioned 

 characters ally it to Ci/clopti/chiiis, but the peculiar form of scale with the postero- 

 inferior angle rounded off, which constitutes one of the main diagnostic marks of that 

 genus, is here absent. Its main specific characters — the tuberculation of the cranial 

 shield, the peculiar sculpture of the mandible, and the non-denticulation of the jiosterior 

 margins of the scales, taken with its size and proportions — are so exceedingly well 

 marked that it may be at once identified even from fragments. 



This species is named after Mr. Arthur Macconochie, of the Geological Survey of 

 Scotland, to whose work in the field is due the discovery of the rich deposits of new 

 fishes and Crustacea in the Lower Carboniferous Rocks of Eskdale and Liddisdale. 



Geological Position and Localities. — Not uncommon in the fish-beds of Calciferous 

 Sandstone age near Glencartholm, Eskdale, Dumfriesshire. The type specimen is in the 

 Collection of the Geological Survey of Scotland, but the example here figured (PI. 

 XXIX, fig. 7) belongs to the Royal Scottish Museum. 



My friend, Prof. Maurice Leriche, of Lille, has noticed and figured^ a small scale 

 from the Upper Carboniferous (Westphalian) of Fresnes in the north of Prance, which he 

 refers to lihadinichfhi/s Macconochii. Certainly his figure shows an astonishing resem- 

 blance to a flank-scale of the species under consideration with the postero-inferior angle 

 broken off. 



1 ' Ann. Soc. Geo). Nord,' vol. xxxvii (1908), p. 270, text-fig. 1, pi. vii, lig. 3. 



