of the Cai'bonifei'ous Period. 7 



flexuous smooth grooves visible to the naked eye, and with 

 distant, irregularly scattered oval foramina. 



The remarkable bony plates to which I have given the above 

 name vary in the number of their sides and the amount of the 

 angles at which they meet ; but the sides are always straight, 

 and the surfaces flat and of uniform thickness. It is clear, from 

 their form, that they cannot belong to the head, but must be 

 viewed as dermal bones, covering some part of the body of a 

 mailed fish. Of known genera they can only be compared with 

 Psmnmosteus of the old red sandstone, to one species of which, 

 the P. meandrinus (Ag.), the resemblance is particularly close, but 

 the ridges of the surface are smooth in the present species and 

 crenulated in the former. The two genera are well- distinguished 

 by the internal microscopic structure, Psammosteus being com- 

 posed of horizontal layers of large irregular cells, while Osteo- 

 plax has well-developed radiated bone-corpuscles. 



Not uncommon in the schists belonging to the base of the 

 carboniferous series at Cultra, Hollywood, county Down, Ireland. 



[Col. Cambridge University.) 



Psammosteus granulatus (M^Coy). 



Sp. Char. A thin, shagreen-like expansion closely covered with 

 nearly uniform hemispherical smooth tubercles, less than half 

 their diameter apart (two in the space of a line), the base of 

 each surrounded by a circle of minute granules. 



This is an irregular fragment of rough shagreen-like integu- 

 ment, measuring about 2| inches in length and \~ inch in 

 width ; it is exceedingly thin. The species is closely allied to the 

 Psammosteus arenatus (Ag.) of the Riga old red sandstone, but 

 is distinguished by the tubercles having no sort of linear arrange- 

 ment, and the granules surrounding the base are proportionally 

 larger and rounder, not seeming like stellular denticles as in 

 that species. 



The specimen is from the fine black shale of the yellow sand- 

 stone (or lowest portion of the carboniferous system) of Kesh, 

 river Banagh, county Fermanagh, Ireland. 



{Col Mr. Griffith.) 



Psammosteus vermicularis (M'Coy). 



Sp. Char. Surface covered with very minute conical tubercles, 

 about six in the space of a line, irregularly placed, but avera- 

 ging their own diameter apart, isolated, or two, three or four 

 confluent to form small, irregularly twisted, vermicular ridges ; 

 the sides of the ridges and base of the tubercles denticulated 

 with angular radiations (as in P. arenatus). 



