BRITISH SILURIAN BRACHIOPODA. 217 



— SiPHONOTRETA, de VemeuU, 1845. 



158. SiPHONOTRETA scoTiCA, Dav. Sil. Sup., PI. XVI, figs. 31—33, 



SiPHONOTRETA SCOTICA, Bav. Geol. Mag., new series, vol. iv, p. 13, pi. ii, figs, 5, 6, 



1877. 



Shell oblong, oval, anterior half broadly rounded, posterior half tapering (in the 

 ventral valve; into an acuminated beak, perforated at its extremity by a small, circular 

 aperture ; valves moderately convex and marked with numerous concentric ridges, 

 from which fringes of closely-packed and adpressed spines take their rise. These tubular 

 spines measure about 1 line in length, are straight and smooth. 

 Length of shell 7 lines by 6 in breadth. 



Obs. — Some few years ago Mrs. R. Gray discovered in the Llandeilo at 

 Craighead and Minuntion, in Ayrshire, several incomplete examples of a Siphojiotreta, 

 differing specifically from S. anglica, Morris, from the Upper Silurian or Wenlock 

 Shale, and from 8. micula, M'Coy, which abounds in the Llandeilo Flags of various 

 English, Scottish, and Irish localities. We are therefore at present acquainted with 

 three British species of SipJionotreta, two of which are characteristic of distinct geological 

 horizons. 



It is not, however, possible, from the crushed and fragmentary condition in which 

 these specimens have been found, to give a complete description of the shell or to establish 

 any satisfactory comparisons between it and the Russian or Bohemian species of the 

 genus. We considered it, therefore, advisable in 1877 to give to the Scottish form a 

 provisional separate name. Much still has to be discovered with respect to the interior 

 characters of this remarkable genus. Some of its internal arrangements have, it is true, 

 been carefully investigated, described, and illustrated by M. de Verneuil, Dr. Kutorga, 

 Dr. d'Eichwald, myself, and others.^ 



The questions relating to its affinities, muscular and other arrangements, present 

 great difficulties, which the material in our possession does not allow us to solve in a 

 satisfactory manner. The form and character of the perforated beak have been well 

 described by Dr. Kutorga. During his visit to Brighton, in 1876, I asked Prof, 

 r. Schmidt if he could procure me a sharply- marked and well-preserved internal cast of 

 the Russian Siphonotreta unguiculata^ and on his return to Reval, in his usual kind and 

 1 'Geol. Mag.,' new series, vol. iv, pi. 11, 1877. 



