J. W. DAVIS ON A BONE-BED IN THE LOWER COAL-MEASURES. 335 



series of the spines, I infer that there can be do sufficient grounds 

 for considering the latter more than a variation from the original 

 type. 



3. Ctenacanthus hybodoides, Eg. 



Tolerably abundant. In good state of preservation. Spines 12 

 to 15 inches long. 



4. Ctenacanthus, sp. ? 



Straight. Ridges much broader than in C. hybodoides, and much 

 fewer in number, being only 5 or 6, whilst C. hybodoides has 16 or 18. 

 The spine presents a fibrous appearance, as though the ganoine had 

 been dissolved away, exhibiting the bony structure underneath. Its 

 length is from 4 to 6 inches. 



5. Ctenacanthus, sp. ? 



This spine differs from the preceding in being more curved, with 

 the ridges symmetrical, and not branching into each other, and 

 closer and finer in appearance. It is 5| inches long, j inch broad 

 at the base, and tapers to a fine point. 



6. Lepracanthus Colei, Egerton. 



Was described by Prof. Owen in the ' Geological Magazine ' for 

 1869, p. 481, from a single specimen found by the Earl of Ennis- 

 killen in the coal-shale at Ruabon. The species occurs in the bone- 

 bed, about a score of specimens having been found. The largest mea- 

 sures 3| inches in length, and ^ 6 - f an inch in width, being an inch 

 longer than the one described by Prof. Owen. He says, "The spine 

 is gently curved, moderately compressed, with the back or convex 

 border rounded ; the thinner concave border is armed by relatively 

 large recurved pointed denticles, subcompressed and strengthened by 

 an almost ridge-like swelling along the middle of each side. These 

 denticles are few in number compared with most similarly barbed 

 fossil fish-spines : four project from about one third of the length 

 of the body of the spine ; and not more than seven are traceable in 

 the present specimen." In one or two of the specimens from the 

 bone-bed, which have left the matrix without being fractured, the 

 spine is seen to have been hollow, with a row of denticles on each 

 side of the concave border; these are placed alternately, and not op- 

 posite to each other, so that there are 13 or 14 denticles, in place of 

 seven as seen by Prof. Owen, one half of the type specimen being 

 hid in the matrix. 



7. Acanthodes Wardi, Egerton. 



Spines of this species are common. They range in size from an 

 inch and a half long, and one eighth of an inch broad, to 7 or 8 

 inches in length, and fully half an inch in breadth. All are 

 characterized by the deep furrow running parallel to the convex 

 portion of the spine. 



