Dr B. H. Traquair on Fossil Fislus from Oil Shales. 125 



measures 2^ inches in length, by ^-^ inch in depth, near its 

 posterior extremity. These proportions would indicate for 

 Mr Gibson's fragmentary mandible, already described, an 

 original length of at least 6^ inches, and somewhere between 

 3 and 4 feet as the probable length of the entire fish to 

 which it belonored. 



Remarks. — This splendid Palaeoniscid seems to have rivalled 

 Acrolepis Bankinei in bulk, with which its remains may also, 

 on superficial examination, be easily confounded. The scales 

 of Elonichthys 2^ecti7iatus may, however, always be easily 

 distinguished by their greater relative thinness, by the 

 narrowness of their covered area, and by the pectination 

 of their posterior margins. These scale-features induce me 

 to class the fish rather in Elonichthys than in Acrolepis, 

 although it agrees with the latter genus in the structure of 

 the pectoral fin. But the small Elonichthys Egertoni also has 

 the principal rays of the pectoral unarticulated for about one- 

 third of their length. The genus Elonichthys will therefore 

 fall into two divisions — the first comprising those species 

 {E. semistriatus, striolatns, tenniserratus, etc.), in which the 

 pectoral rays, except one or two short ones immediately on 

 the lateral edge of the fin, are all articulated up to their 

 origins ; and the second those other species (E. Egertoni, 

 Portlockii, pectinatus) in which the principal rays of the fin 

 are unarticulated at their origin for about one-third of their 

 length. The second division forms a transition to Acrolepis. 



(5.) Eurynotus sp. 



On a slab of shale in the collection at the West Calder Oil 

 Works there are numerous scattered scales of an Eurynotus, 

 which I cannot distinguish from those of E. crenatus. Mr 

 Stock also possesses a small and not very perfect specimen 

 of Eurynotus preserved in an ironstone nodule, from a pit in 

 the vicinity, concerning which it is better at present to ex- 

 press no opinion as to species. 



(6.) Gyracanthus tuberculatus, Ag. 



A considerable portion of a large spine, lent to me by Mr 

 D'Arcy W. Thompson, who obtained it from the West Calder 



