A. Harker—Blue Hornblende. 455 
That this large and apparently once thin and tough bivalved 
specimen should have been referred to by Mr. Salter as belonging 
probably to the Phyllopoda would go far to induce us to support his 
view, if we knew of any analogous form among that group. As 
a bivalved Crustacean, however, the apparently equal ends of the 
valves, and their radiating furrows, are out of place or quite abnor- 
mal. If looked at as an Apudiform or buckler-shaped form, folded 
down the middle, the same objections occur. The probable slit at 
each end would serve for either case, though not quite fitting with 
the latter. 
It is less difficult to find an analogue for this specimen among the 
Bivalved Molluscs. Thus Siliqua radiata, Linn., has a straight, feeble 
hinge-line, and concentric striz, but radiating colour-lines instead of 
furrows. In Soletellina violacea, Lamarck, the hinge and umbo are 
stronger than in the foregoing; there are concentric striz, and the 
radiating faint, colour-lines, are slightly raised. Both Pholas and 
Pholadomya, of course, have transverse ridges and furrows somewhat 
analogous to those of our fossil, but their other features do not 
coincide. Clidophorus has a straight hinge and radiating riblets ; 
but the latter start from an umbo near one end; and the valves 
have a shape different from that of the specimen under notice. 
Having thus noticed this interesting specimen, we must for the 
resent leave its more definite generic relations indeterminate, hoping 
that fresh material may turn up through the energy of local observers 
and collectors whose attention is now again called to it. Although 
at present the position of this fossil must remain doubtful, yet, for 
the sake of convenience of reference and cataloguing, it may in 
future be known as Salterina pholadiformis, Salter, sp. 
VI.—AppitionaL Note on tHE Biue HornpuenpE or Mynypp 
Mawr. 
By Atrrep Harker, M.A., F.G.S., 
Fellow of St. John’s College, Cambridge. 
N the short description of the Mynydd Mawr rock given in the 
May Number of this Macazine (p. 221), I drew attention to a 
remarkable blue hornblende, which I was unable to refer to any 
kiown variety. In the character of its absorption and pleochroism 
it differed widely from both glaucophane and arfvedsonite, although 
allied to them in some of its properties, such as its extreme fusibility, 
sjlinters melting easily in the flame of a candle. 
A paper by Dr. Sauer of Leipzig, which has just appeared,’ 
tlrows considerable light on the subject, and makes it appear that we 
hive here a new mineral of considerable interest. Among the rocks 
edlected in the island of Socotra by the late Dr. Riebeck is a pink 
fespar-granite containing black crystals up to 5 mm. in length. 
Tiis is the mineral which has been named Riebeckite in honour of 
tle traveller, and which presents the closest resemblance to that 
ocurring in the quartz-porphyry of Mynydd Mawr. It has been 
1 Zeitsch. d. Deutsch. geol, Gesellsch. vol. xl. p, 138, 1888. 
