222 THE CANADIAN NATURALIST. [June 



GEOLOGY AND MINERALOGY. 



Cephalaspis Dawsoni. — Mr. E. Ray Lankester describes this 

 species in the Geological Magazine for September as follows : — 



Principal Dawson, of Montreal, Canada, has placed in my 

 hands for description a remarkably interesting specimen, indicat- 

 ing a species of the genus Cephalaspis in transatlantic Silurio- 

 Devonian beds. He writes, " The specimen was found by one of 

 my assistants, Mr. G. T. Kennedy, B.A., when collecting with 

 me, in a bed charged with remains of Psilopliyton, on the north 

 side of Gaspe Bay. The geological horizon is below the middle 

 of the Gaspe Sandstones, but several hundreds of feet above their 

 actual base, so that the specimen may be regarded as either 

 Lower Devonian or Lower Middle Devonian. It occurred in beds 

 containing PsUopliyton 2}rinceps and P. rohustus, and also drift- 

 trunks of Prototaxites Logani, the latter in the sandstones asso- 

 ciated with the coarse shaly bed containing the Cephalaspis. In 

 these sandstones there are also spines of Macliairacantlius sulcatus 

 of Newberry — a large fish characteristic of the Devonian of Ohio. 

 No marine remains were found in the bed holding the Cephalaspis^ 

 which is blackened with vegetable matter and holds many frag- 

 ments of land plants ; but in shales at no great vertical distance 

 there are shells of Lingula and 3Iodiomorpha, resembling species 

 found in the Hamilton group of New York." 



The specimen presents in slight relief a small Cephalaspis, with 

 head-shield and greater part of the body, and is much flattened. 

 The shield appears to be larger in proportion to the body than in 

 any British species. The orbits are not shown, and the matrix 

 has not preserved the scales of the body with much distinctness? 

 though it is possible to make out the lateral and marginal series. 

 No trace of pectoral, dorsal, nor caudal fins is to be made out. 

 This species clearly belongs to the section Eu-cephalaspis as 

 defined in my Monograph of Cephalaspiclce. Its best character 

 as a species is to be found in the very fine, almost granular, tuber- 

 cles which are preserved on some parts of the surface, and repre- 

 sent the apparently universally present tubercular ornament of the 

 Osteostraci. These fine tubercles are more minute than on any 

 British CephaJaspid, and, though seemingly not very well shown 



