BRITISH DEVONIAN BRACHIOPODA. 87 



the Silurian Cyrtia eocporrecta of Wahlemberg. It differs from Sp. simplex by the 

 presence of a well-defined mesial fold. Its narrow-arched deltidium is partly seen in one 

 specimen. The largest and best examples are preserved in the Torquay Natural History 

 Museum, and were kindly lent to me, with many more species, by my old and valued 

 friend Mr. W, Pengelly. Several specimens were also found by Mr. Whidborne, after 

 whom it gives me much pleasure in naming the species. They are all from the Middle 

 Devonian of Lummaton, near Torquay. 



Genus — Cyrtina, Davidson, 1858. 



25. Cyrtina heteroclita, Bef., sp. Dav., Dev. Mon., PI. IX, figs. 1 — 10; and Dev. 



Sup., PL I, figs. 35, 36, 37. 



When describing this important species in my ' Devonian Monograph ' I was not 

 acquainted with its spirals or their attachments. Prof. King, in vol. iv, pp. 254 — 256, 

 of the ' Geological Magazine,' 1867, describes and figures the perforated shell-structure 

 of Cyrtina heteroclita, and adds that one of his specimens exhibited the spiral appendages 

 very distinctly, but he gives no figure of them. In 1853 Dr. Carpenter stated that he 

 had determined the existence of perforations in the shell under description. In 1871, 

 in tab. 52 of his ' Die Brachiopoden,' Prof. Quenstedt gave a figure of Cyrtina 

 Jieteroclita, in which one of the spirals is drawn. Recently the Rev. Norman Glass 

 has experimented on a large number of specimens procured by Mr. G. F. Whidborne 

 from the Middle Devonian at Lummaton, near Torquay, and has been able to develop 

 the spirals and their connections. After being attached to the hinge-plate, the two 

 primary lamellae extend to within a short distance of the front before forming the first 

 convolution. About their middle they are connected by a Y-shaped lamella. The 

 spiral coils also vary a good deal in their direction, but in general each spiral cone is 

 directed upwards, and extends for some distance into the rostral cavity of the ventral 

 valve, as may be seen in Sup., PI. I, figs. 37, 37«. Each spiral seems composed of from 

 ten to twelve convolutions. 



Mr. Glass informs me that the specimens of Cyrtina heteroclita from Lummaton are 

 composed of a light-coloured limestone, which seems to be of a somewhat sparry nature, 

 and which when worn thin at any part becomes semi-transparent. Many of the 

 Terebratuloid specimens from the same locality are composed of a similar material, 

 which is easily worked with the knife. The spirals of Cyrtina heteroclita were developed 

 by first splitting the specimen in half from the umbo to the anterior margin, and then by 

 working out the spiral in each fragment separately, and as a transparency. In another 



