DUBLIN MICROSCOPICAL CLUB. 



347 



to designate iV. Mossiana as follows: Valve broadly elliptical, 

 leugth 0027", breadth "00 LS"; median line well-marked, lying 

 in a narrow, unstriate, Imear space, with a wide quadrangular 

 expension around the central nodule ; striae distinct, close, 

 punctate, slightly radiate in the middle, more and more decidedly 

 radiate towards the ends; tovvards the mid lie of the valve the 

 lines of puucta are interrupted, so as to form on either side of the 

 median line two or three distinct longitudinal bands, nearly 

 parallel to the median free space. Schmidt has figured without 

 Dames some forms which stroigly resemble the present, ' Atlas 

 der Diat.,' t. vi, figg. 35, 36, 39. 



2'7tk February, 1878. 



A New Mineral from Carnmoney Hill, near Belfast, exhibited. 

 — Professor Hull, F.K.S., exhibit3d a thin section of the Olivine 

 Basalt of Carnmoney Hill, near Belfast, containing a mineral 

 considered by Mr. E. T. Hardman, F.C.S., who has analysed it, 

 to be new. Tlie mineral is black, glossy, and gives an olive- 

 brown streak; hardness 25, sp. gr. 1609 — 1700. It occurs aa 

 a material filling cells and cavities in the original rock and often 

 surrounding the crystals of felspar, olivine and augite. It is in 

 a gelatinous, uncrystalline condition, and does not polarize under 

 the microscope ; with a low power it is seen to be of a chocolate 

 or yellowish-brown colour, passing into black in the thicker por- 

 tions of the slice. No special structure is observable, but with a 

 high power faint, wavy lines, like those of stalg mite or chalcedony, 

 were observed, giving evidence of a formation from aqueous solu- 

 tions. The author had no doubt, both from the characters of this 

 mineral under the microscope and from the chmical a!ial>^sis of 

 Mr. Hardman, that it was a secondary mineral, derived from 

 aqueous solution after the rock had consolidated from the crys- 

 talline state. 



The following is the analysis : 



Silica 



99-848 per cent. 



A New Variety of Stysanus stemonitis, exhibited. — Mr. Pirn 

 showed a remarkable mould which grew on a bamboo-stake in 

 his hothouse. It bore no resemblance to any mould figured in 



