BRITISH SILURIAN BRACHIOPODA. 115 



cation of that of Atrypa reticularis and A. marginalis, and that with this genus A. Barrandei 

 should be classed. Thanks to the kindness of Mr. Whitfield I have been able to examine 

 nine or ten typical specimens of Professor J. Hall's Ccelospira dlsparialis from the Niagara 

 group, Lockport, New York. In dimensions the specimens forwarded were a little 

 smaller than full-grown examples of Atrypa Barrandei, and their dorsal valve was gene- 

 rally a little more concave. Mr. Whitfield also kindly sent for my examination the only 

 specimen he had been able to develop of the American shell. It agrees in every respect 

 with the figures we have given of the spirals of Atrypa Barrandei. 



In 1852 Professor Hall described the American species with the name Atrypa 

 disparialis, ' Pal. New York,' vol. ii, p. 277. In the ' Tenth Annual Report of the State 

 Cabinet of Nat. Hist, of New York' he altered the generic name to Leptocceiia, 1857 ; 

 and in the ' Twenty-eighth Annual Report,' p. 162, 1879, he referred the genus to 

 Ccelospira, adding that this species is comparatively rare, and stating that " The specimens 

 from the Waldron locality show considerable variation in form, convexity of valves, and 

 number of plications. Compared with specimens of Betzia Barrandei (Davidson, 1848) 

 from Dudley, England, they seem to be very closely related, if not identical." In these 

 conclusions I quite agree with Professor Hall, but at the same time would place both A. 

 Barrandei and C. disparialis with the genus Atrypa. In Bohemia Atrypa Barrandei was 

 found by M. Barrande in his Stage E. at Hinter-Kopanina. The Bohemian specimens 

 are exactly of the same size as those that occur in England. 



14. Atrypa imbricata, Sow. Dav., Sil. Mon., PI. XV, figs. 3 — 8; and Sil, Sup., 



PL IV, fig. 7. 



At p. 135 of my ' Silurian Monograph ' this species is fully described, and I stated 

 that interiorly two broad coiled lamella? are attached to the hinge-plate, with vertical 

 spires, closely adpressed, and directed towards the disc of the valve. At that period I 

 had no specimen I could figure, but since then the Rev. Norman Glass has made a 

 section through one of them showing exactly the position of the spires, and of this a 

 figure has now been given. 



