634 REPORT— 1881. 



3. On 'Flots.' By J. R. Dakyns, M.A., Geological Survey of England 



and Wales. 



The word 'flot' is a miner's term for ore lyinp' between the beds, or at certain 

 definite horizons in the strata. In textbooks flots are p:enerally called 'flats' 

 or ' flattings.' The}^ are of two kinds: (1) those connected with 'cross-veins'; 

 (2) those connected witli courses of dun limestone. Firstly, cross-veins are 

 veins (generally mere spar veins on Greenhow Hill) Avhich cross and intersect 

 or shift the metal veins, but which often bear ore at their intersection with 

 the metal veins. Where these cross-veins cut the flot-planes, ore is found. 

 Secondly, similarly with courses of dun limestone. Dun limestone, so-called from 

 its colour, is a dnlomitized form of ordinary limestone. The dun lime occurs in 

 beds or irregular masses, or more frequently iu dyke-like courses, running N.N.W. 

 and S.S.E. These courses are often several yards or even fathoms wide, and 

 where the dun course crosses the flot-plaue ore is developed along the joints 

 between the dun and the white limestones. 



Ore is not found along the flot-plane except at its intersection with the cross- 

 veins or with the courses of dun limestone. 



4. RemarJcs uj^on the Strudin'e and Classification of the Blastoidea. 

 By P. Hekbekt Caepentee, M.A. 



The author and Jlr. R. Etheridge, jim., who are preparing a joint Memoir 

 upon the Blastoidea, have arrived at the following conclusions respecting the 

 group. 



It is very doubtful whether the genus rentremites occurs at all in Britain. 

 Some badly preserved fragments from the Devonian and the Scotch Carboniferous 

 are possibly referable to it ; but most of the Blastoids (besides Cadaster) which 

 occur in the Carboniferous Limestone belong to the genus Granatocrintts, Troost., 

 which is represented by some seven or eight species. 



Cumberland's 3Iitra eUiptica is the representative of a new genus, distin- 

 guished by the eccentric position of the spiracles. Codastcr is a true Blastoid, and 

 not a Cystid, as supposed by Billings, Tlie slit-like openings of its hydrospires are 

 nearly on the same level as the ambulacra, which do not conceal them at all. In 

 the ordinary Blastoids, however, they are below and concealed by the ambulacra, 

 opening externally by pores at the sides of the latter. There are various interme- 

 diate forms between these two extremes, in which the hydrospiral slits are more 

 or less concealed by the ambulacra, but are partially visible at their sides. It is 

 proposed to group the species thus distinguished into a genus Fentremitidea, which 

 is represented in Britain by the little Pentrcmitcs acutus, Sowerby, in Belgium by 

 P. caryopJiyllatus, and in Spain by P. PAilleti, De Verneuil, for which last the 

 uame PentrcmHidva had been already proposed by D'Orbigny. An arrangement 

 of this kind has been already suggested by I3illings. 



The discoveries of Eofe, Wachsmuth, and Ilambach, respecting the perforation 

 of the lancet-piece by a longitudinal canal, are confirmed. This canal probably 

 lodged the water-vessel, which must have been devoid of any tentacular extensions, 

 as in some Ilolothurians, and in the arms of certain Cornatidce. Respiration was 

 effected, however, by means of the hydrospires. The pores usually found at the 

 sides of the ambulacra were not the sockets for the attachment of the appendages, 

 but led downwards into the hydrospires, serving to introduce water, which made 

 its way out through the spiracles. The genital ducts probably opened into some 

 portion of the hydrospires, as they do into the closely similar structures of the 

 Ophiuroidea, and the ova were discharged through the spiracles. Billings' 

 statements are confirmed respecting the existence in many species of a single or 

 possibly double row of jointed appendages along each side of the ambulacra; but 

 these appendages are not homologous with the pinnules of the Crinoidea. 



In perfect specimens the peristome is covered in by a vault of small polygonal 

 plates, any definite arrangement of which is rarely traceable. Extensions of this 



