108 



REPORT 1872. 



These liave a more extensive range, Didycniema lasting from the Cambrian to the 

 Devonian period ; but until now they were only known to occur together and in 

 any abundance in the Quebec rocks of Canada. They have, however, recently 

 .been discovered by the author in the Arenig rocks at Shelve. A few specimens, 

 apparently referable to the genus RetioUtes, have also been found. This genus 

 begins in "the Quebec group (Arenig), and ranges upwards to the highest beds of 

 the Caradoc or Bala rocks. 



Of the species many are new ; but all hitherto described are entirely restricted 

 to the Arenig group. All these occur in the Canadian rocks ; but only two {IJidy- 

 moc/rapsus putulus and Tetra(/rapsus serra) have previously been recorded from the 

 Arenig rocks of Britain. The entire Graptolite fauna is thus, in its species as well 

 as in its genera, more nearly allied to that of the Canadian Arenig rocks than to 

 our own Arenig faunas in Cumberland and Shropshire. 



The species, of which specimens were exhibited, are as follows : — 



Didymogi-apsus extensus, Hall. 



patulus, Hall. 



penuatulus. Hall, 



plumula, sp. nov. 



sparsus, sp. nov. 



Tetragrapsus serra, Brongn. 

 Logauograpsus(?) implicatus, sp. 



nov. 

 Phyllograpsus stella, sp. nov. 

 Retiolites ensiformis (['), Hall. 

 Ptilograpsus cristula, sp. nov. 

 Hicksii, sp. nov. 



Deudrograptus arbuscula, sp. nov. 

 {Salter, MS.). 



divergens. Hall. 



flexuosus. Hall. 



pumilus, sp. nov. 



■ striatus, Hall. 



Callograptus (?) diffusus, Hall. 



elegans. Hall. 



radiatus, sp. nov. 



radicans, sp. nov. 



Salteri, Hall. 



Dictyouema caucellata, sp. nov. 



A specimen of Callopraptus radiatus, with an entire " hydrocaulus," or main stem, 

 and a " hydrorhiza," the organ of attachment, was specially alluded to as furnishing 

 an important addition to our knowledge of the mode of gTowth of the dendroid 

 Graptolites. The hydrorhiza appeared as a series of interlacing or anastomosing 

 fibres, which must have formed a kind of network over the surface to whicii it 

 adhered. Its presence in this specimen was considered to prove it to be an essential 

 organ of the genus CuUograptus, its rarity being accounted for by its perishable 

 nature, and the probability of the Graptolite being almost invariably severed from 

 the substance to which it was attached at the junction of the hydrocaulus with its 

 hydrorhiza. 



" The other dendroid Graptolites (Ptilor/rapsi/s, Deiulrofiraptus, and Didyonetnd) 

 were also shown to have been most probably fixed forms. 



On the Minerals lately found in tJie Drainage-ivorlcs at Brit/Jiton. 

 By James Howell. 



The author exhibited curious and beautiful specimens of minerals found in the 

 north-west portion of Brighton, the Montpellior district, during the excavations 

 for the main sewer. These excavations were carried through beds overlying the 

 chalk, down into the chalk itself, to a depth of from 22 to -30 feet. The surface- 

 beds consisted of vegetable mould, loam, and brickearth, the latter reaching in 

 many places to the depth of 17 feet. Imbedded in this deposit were masses and 

 veins of Websterite, mingled with brecciated masses of ironstone, flints, gypsum, 

 and indurated clay, frosted over and permeated witli crystals of selenite, varying 

 in form and colour, and presenting a beautiful appearance. There were also tabular 

 flints, probably a silicate of iron about f of an inch in thickness, coated with a 

 carbonate of lime, with nodular flints shivered in every direction, and recemeuted 

 by the Websterite. Some of the breccia, lying at the depth of 17 feet, so much 

 resembled " slag " as to deceive the eyes of good mineralogists. Most of it 

 had undergone intense chemical action, as if the gases had bubbled up and 

 escaped, leaving orifices upon the surfiice, or presenting a botryoidal aspect. Some 

 of the ironstone presented a honeycomb appearance, being of a black or dark 



