BRITISH SILURIAN BRACHIOPODA. 103 



Genus— Meuista, Suess, 1851. Dav., Sil. Sup., PI. V, figs. 10 to 13. 

 Davidson, On the Genus Merista, Geol. Mag., New Series, vol. viii, p. 289, 1881. 



In his memoir, ' Brachiop. der Kossener Schichten/ p. 17, Professor E. Suess proposed 

 his genus Merista, giving as its type the M. Herculea, Barrande ; and at p. 85 of the 

 German edition of the General Introduction to my work on ' British Fossil Brachiopoda ' 

 Professor E. Suess redescribes his genus, and in pi. iii figures its spirals and shoe-hfter 

 process ; but neither the connections of the spirals nor their attachments to the hinge- 

 plate had then been discovered. Professor Suess also includes in his genus Merista 

 the Whiffieldia {Atrypa) tumida of Dalman, the internal and differential characters of v\^hich 

 were then likewise unknown. In our Devonian rocks the genus Merista is represented 

 by the Merista plebeia or scalprum ; but, although Mr. Glass was able in several specimens 

 to develop its spirals, he entirely failed to expose its loop, on account of the difficult 

 nature of the limestone or opaque spar which fills most of the specimens. 



Considering it to be very desirable that the internal characters of this important genus 

 should if possible be discovered, I wrote to my old and valued friends, M. Barrande and 

 Prof. Kregie, of Prague, and to Professor Suess, of Vienna, requesting them to kindly send 

 me some specimens of Merista Herculea, that the Rev. Norman Glass might endeavour 

 to work out the loop and the attachments to the hinge-plate which had not been 

 hitherto discovered ; and, thanks to his great skill and patience, we are now acquainted 

 with the whole characters belonging to the genus under description. 



We are not positively acquainted with any certain representative of the genus in our 

 British Silurian rocks, unless Merista ? cymhula and M. ? Circe belong to the genus. The 

 well-developed shoe-lifter process in the former is that of Merista ; but we are not 

 acquainted with its spirals or their connections, and I have not been able to procure 

 specimens of it suitable to Mr. Glass's operations. We have therefore to describe the 

 internal character of the genus from our examination of foreign examples of the type, 

 Merista Herculea of Barrande. 



The principal stems forming the spirals are attached to the hinge-plate {a) ; 

 thence they proceed for a short distance into the interior of the shell with a very gentle 

 inclination forwards, and at d they are abruptly bent backwards at an acute angle 

 towards the bottom of the lateral portions of the beak. Thence they form a broad 

 rounded curve facing the bottom of the dorsal valve (c), and after converging to about 

 half their length again diverge towards the front, and thus form the first spiral coil ; 

 again at about half their length (at d) the principal lamellae widen and give off another 

 lamella. These lamellae converge from both sides towards the middle of the interior of 



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