RHADINICHTHYS (?) ANGUSTULUS. 101 



Description. — The following description is taken from two specimens in the collection 

 of the Geological Survey of Scotland, one of which, the larger and less perfect, measures 

 2| inches in length, while the other and more perfect example (PI. XXXVI, fig. I) 

 attains a length of only 1£ inches. The length of the head is equal to about one-quarter 

 of the total ; the greatest depth of the body is at the shoulder, and is contained about 

 six times in the entire length of the fish, while it is not so much as twice the depth 

 of the tail-pedicle, the dorsal and ventral margins being nearlv straight. The general 

 contour is therefore peculiarly short and straight, and wanting in the usual more or less 

 fusiform outline, while the tail-pedicle is of great proportional depth. 



All that can be said of the head is that it is typically Pala^oniscoid in structure, with 

 oblique suspensorium, etc., and that some traces of a minute ridged ornament are seen on 

 some of its delicate bones, e.g. the mandible. The body-scales (fig. 2) are of moderate 

 dimensions in proportion to the size of the fish, and are marked each with three or four 

 delicate, yet sharply defined, and somewhat distant ridges, which run right across the 

 outer surface of the scale from before backwards, parallel with the superior and inferior 

 margins; on the minute lozenge-shaped scales of the caudal body-prolongation these 

 ridges, now excessively fine, are diagonal in position. The V-scales of the tail are 

 proportionally largely developed. 



The pectoral and ventral fins are small, the dorsal and anal nearly opposite, though 

 the former arises a little in advance of the latter. The two last-named fins resemble 

 each other in their triangular-acuminate contour; the caudal is not completely preserved, 

 but its appearance seems to indicate that it was bifurcated in the usual manner. The 

 tins are preserved only in the smaller of the two specimens, and their rays are so 

 excessively delicate that, it is impossible to describe their articulations, but they are closely 

 set, and appear to bifurcate towards their extremities. 



Observations. — On account of its general structure, so far as can be made out, along 

 with the form and position of the fins, though the condition of the rays of the pectoral 

 cannot be established, this strange little fish may be placed, at least provisionally, in the 

 genus Rhadinichthys. As regards the scales, a somewhat similar sculpture may be seen 

 on those of various other Carboniferous Palaeoniscidse, such as Elonichthys microlepidotiis 

 and E. striatulus, Rhadinichthys Grossarti and Styracopterus fulcratus, but the present 

 species is distinguished from all these by obvious details of form. It seems to be 

 somewhat rare; two specimens are in the collection of the Geological Survey of Scotland, 

 while another is noted by Dr. A. Smith Woodward as belonging to the British Museum. 



Geological Position and Locality.— Only known as yet from the fish-bearing shales 

 of Calciferous Sandstone age exposed in the banks of the Kiver Esk near 

 Glcncartholm. 



