280 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 18, 



2. Palichthyologic Notes. No. 5. — On two new species of 

 Placoid Fishes from the Coal Measures. By Sir Philip 

 DE M. Grey Egerton, Bart., M.P., F.R.S., F.G.S. &c. 



[Plate XII.] 



Some years have now elapsed since I first became aware of the occur- 

 rence of a large species of Cestraciont in the shale-beds of the Lanark- 

 shire coal-field ; but I have postponed from time to time the task of 

 describing it, partly from an unwillingness to rush before the public, 

 on the discovery of each new species, with inconsiderate haste in the 

 general scramble for priority of credit, now, I regret to say, so much 

 the vogue, but principally in the hopes that some cognate materials 

 might come to light to render the communication more worthy of the 

 time and attention of the Society. The recent discovery of a second 

 species, and the increased and increasing interest which the researches 

 of the last few years have imparted to the fauna of the Carboniferous 

 epoch, may perhaps now be considered a sufficient justification for the 

 present memoir, meagre though it be. 



The first specimen which attracted my attention to this subject 

 was a defence-bone discovered by a collector named Doran in the 

 black shales of the Carluke district. This is now in the British 

 Museum. Similar rays have since been found in several localities. 

 The Museum of Practical Geology possesses specimens from the 

 Talwyn works, near Mold in North Wales, in shale ; and from Hady, 

 near Chesterfield, in ironstone. And Lord Enniskillen and myself 

 have several very perfect examples from the neighbourhood of Dal- 

 keith, where they are associated with finer specimens of Gyracanthus 

 spines than I have seen from any other locality. 



Ctenacanthus hybodoides. — The most perfect specimen I 

 have seen of this species (Plate XII.) is contained in a slab of black 

 compact shale from the Dalkeith district. It measures 9^ inches in 

 length, 7 inches being external, and 2^ inches imbedded in the inte- 

 guments. The proportion of the latter to the former is smaller than 

 is usual in the Ichthyodorulites of the Oolitic age. The greatest 

 width of the spine is 1|^ inch. On quitting the body of the fish this 

 spine is nearly straight for half its length ; it is thence slightly re- 

 curved. The angle it forms with the line defining the integumentary 

 investment is about 4.)°. The external portion is elegantly ornamented 

 with frequent parallel longitudinal ridges, greatly resembling the 

 characteristic ornamentation of the dorsal spines of the Hybodi. 

 They are about eighteen in number at the base, but diminish to 

 twelve at the apex. Those on the anterior and middle regions of the 

 spine are continuous throughout its entire length, but the remainder 

 die out as they reach the posterior angles. A double row of small 

 tubercles, extending from the base to the apex on either side, defines 

 the junction of the lateral with the hinder area of the bone. This 

 tubercular character is traceable, but in a less degree, on all the lon- 

 gitudinal raj^s as they approach the extremity of the fin. I have 



