86 SUPPLEMENT TO THE 



In PL VIII of my General Introduction there are figures showing clearly the position 

 and shape of the spirals in Koninckina. Figures of these spirals will be found also in 

 PI. Ill of the German edition of my General Introduction. The shape of the spirals, 

 as far as the incomplete specimens show, seem similar to those of Thecospira. In this 

 last the apex of the spiral coils faces the bottom of the middle of the ventral valve. 



Figures of the spirals of Davidsonia will be found in PI. XI of my 'Devonian 

 Monograph.' In this genus, as in Atrypa, the apex of the spiral cone is directed towards 

 the bottom of the dorsal valve. 



The third division includes Glassia and Zygospira. In these genera the extre- 

 mities of the spiral coils face each other towards the middle of the shell. In Glassia, as 

 will be seen further on, the principal stems of the spiral coils are connected, as in Atrijpa, 

 while in Zygospira the principal lamellae are connected lower down by means of a long 

 curved band. 



Mr. Glass's description of his modus operandi in developing the loops and spirals, to 

 which he has given so much time and labour, will here precede my description of the 

 genera and species of the spiral-bearing Brachiopoda. 



On the Development of the Spiirals and their connections in the Palaozoic Brachiopoda. 

 By the Rev. Norman Glass. 



" In May, 1860, I had the pleasure of discovering at Pen-y-llan, near Cardiff, the 

 furthest Silurian outlier in that direction. Sir Roderick Murchison requested me to 

 send him a number of fossils I had collected in this locality, and on their inspection he 

 declared them to belong par excellence to the Wenlock Limestone. Amongst these 

 fossils, which he termed ' very beautiful,' was a specimen of Meristella tumida, showing 

 the spirals coated with crystallised carbonate of lime, and in a very perfect state of 

 preservation. 1 had previously seen Mr. Davidson's figures of the spirals of Sjnrifera 

 striata and Athyris pectinifera, &c. ; but, though I had worked for some years amongst 

 the Carboniferous and Silurian Rocks, it had never been my good fortune to find any 

 trace of the spiral appendages. Some of my friends, who had great experience in 

 collecting, had been equally unsuccessful in this respect, and it seemed to us — and, indeed, 

 this was the general opinion — that specimens showing the spiral appendages of the 

 Brachiopoda were extremely rare. The specimen of Meristella tumida referred to above 

 was embedded in the surface of a mass of friable rock, and was itself evidently full of 

 fractures, the spirals being apparent owing to a small fragment of the dorsal valve having 

 been displaced. Experienced collectors can imagine the interest, blended with anxiety, 

 with which I regarded this remarkable find. The slightest touch would apparently 

 cause it to fall to pieces, and it was only by carefully carrying it in my hand, matrix and 



