Correspondetice — Fossil Beads. 



141 



Out of the large series of 2,902 specimens of Porosphcera exaaiined 

 and determined by Dr. Hinde, about two-thirds, he says, were 

 obtained by Dr. A. W. Rowe, F.G.S., whose researches on the fossils 

 of the different zones of the Chalk of England have become a classical 

 work to' all students of Cretaceous geology. In Dr. Hinde's opinion 

 we find only 3 examples named Porosphcera Woodwardi, Carter, sp., 

 from the Lower Chalk (Cenomanien) of Dover and the Dorset coast. 

 109 were obtained from localities in the Middle Chalk (Turonian), 

 99 of which are referred to P. glohularis, 3 to P. patelliformis, and 

 7 to P. arrecta. But the majority of specimens, 2,770, were obtained 

 from the Tipper Chalk (Senonian), which yielded 2,244 examples of 

 P. glohilaris, 257 of P. nuciformis, 149 referred to P. pileolus, 94 to 

 P. patelliformis, 7 to P. arrecta, and 19 to "irregular forms of 

 PorosphcBra'''' \ while of zones unknown, 14 are referred by Dr. Hinde 

 to P. glolularis, 1 to P. pileolus, 4 to P. patelliformis, and 1 an 

 irregular form. In all, 2,902 were examined and determined by 

 him, of which 2,357 are referred to P. glohularis and 545 to the 

 six other species. If we except the Lower Chalk, P. glolularis 

 occurs throughout the Middle and Upper Chalk, and is very abundant 

 at Dover ; in Devon, Seaford and Newhaven, Croydon, Margate, 

 Brighton, Sewerby, and on the Dorset coast. These localities do 



Fig. 2. Porosphcera glohularis, Phillips, a small bead-like fossil sponge, derived 

 from the Chalk, and found abundantly in the old river-valley gravels of 

 Bedfordshire. The above figures are reproduced from an article by 

 Mr. James Wyatt, F.G.S. (see the Geologist, vol. v, pp. 233-5, 1862). 



not include the vast number met with in the Bedfordshire gravels 

 and elsewhere derived from the Chalk, whilst it is abundant in the 

 gravels at Amiens and Abbeville in France, and is present almost 

 everywhere in the Chalk of Middle and Northern Europe. Dr. Hinde 

 adds : " In form these sponges are genei'ally rounded like peas or 

 marbles, but are sometimes oval, loaf- or cushion-shaped, without any 

 distinctive base ; they are mostly free and unattached, but in many 

 cases they grew round foreign bodies, which have been incapable of 

 fossilisation^, and these sponges now exhibit cylindrical liollow tubes 

 which extend partly or entirely through them [see 1, Fig. 1]. 

 Generally increase of growth is uniform over the surface, but in some 

 instances fresh layers are formed so as only to cover portions of the 

 surface at once [see 4, Fig. 1]. Small specimens are found of about 

 1mm., the larger forms range to 34 mm. in diameter." (Op. cit., 

 p. 19.) 



In another place (p. 11) Dr. Hinde says: "Numerous specimens of 

 P. glohularis, and also of P. nuciformis, are penetrated by cylindrical 



