192 SUPPLEMENT TO THE 



Gemis — Strophomena, Bofinesque. 1820 or 1825 ? 



Very little new has been discovered with respect to the species belonging to this 

 genus since the publication of my ' Silurian Monograph,' but some additional details 

 have been gleaned in connection with some of those already described and which occur in 

 Scotland. 



114. Strophomena rhomboidalis, Wilckens, sp. Dav., Sil. Mon., PI. XXXIX, figs. 



1—21; and PI. XLIV, fig. 1. 



This well-known and far-spread species has, in Scotland, been found to range from 

 the Llandeilo to the Ludlow inclusive. Mrs. R. Gray obtained it from the Llandeilo, 

 at Craighead ; the Middle Caradoc, at Shallock Mill ; from Thraive, in the Upper 

 Caradoc ; at Mulloch Hill, in the Lower Llandovery ; in the Middle Llandovery, at 

 Newlands and Woodland Point ; in the Upper Llandovery or Penkill Beds, at Penwhapple 

 Glen ; all in Ayrshire. It has also been found in the Wenlock and Ludlow rocks of the 

 Pentland Hills. 



115. Strophomena corrugatella, Dav. Sil. Mon., p. 301, PI. XLI, figs. 8 — 14 ; Sup., 



PI. XV, figs. 23—26. 



This beautifully sculptured species has been collected in Scotland in the five following 

 horizons: — In the Llandeilo, at Balcletchie ; in the Middle Caradoc, at Shallock Mill; 

 at Drummock, in the Upper Caradoc; at Benan Craig, in the Lower Llandovery; 

 and at Woodland Point, in the Middle Llandovery ; all in Ayrshire. It has also been 

 obtained by the Geological Survey of Scotland at Black Burn, Wanlock Water, Leadhills 

 District, Dumfriesshire. 



Strophomena corrugatella attains largest dimensions at Woodland Point, in the Girvan 

 district, and shows strongly-marked wrinkles near the cardinal edge. 



116. Strophomena Shallockiensis, Dav. Sil. Sup., PI. XI, figs. 20, 21 ; PI. XII, 



fig. 30 ; and PI. XVI, fig. 8. 



Semicircular, wider than long, hinge-line straight, about as long as the breadth of 

 the shell ; dorsal valve uniformly and gently convex, hinge-area narrow ; ventral valve 



