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Genus — LEPTjENA, Dolman. 
1. LEPTiENA ? INTERSTPIxVLIS, J. DMllips. 
Orthis interstrialis, J. Phillips, 184*1, Pal. Poss. Cornwall, p. 61, pi. 25, fig. 103. 
Leptcena interstrialis ? Schnur, 1853, Beschr, Uebergaugsgebirge Eifel Braeh., p. 51, pi. 
20, fig. 2. 
,, interstrialis, T. Davidson, 1865, Mon. Brit. Dev. Brach., p. 85, pi. 18, fig. 15-18. 
Sliell usually transverse, semicircular, greatest widtli at the hinge line 
the ends of which are angular and extend a little beyond the sides. The 
ventral valve is fairly regularly convex while the ventral [dorsal] is concave 
and follows at a small interval the curvature of the other. The principal 
characteristic is comprised in the surface ornamentation, which is composed 
of some numher of delicate ribs (twenty to twenty-four) having their origin 
at the beak and directing radiatingly towards the edges. At some distance 
from the beak, and in the middle of the clear space between two contignous 
primary ribs, are developed others a little thinner than them which also extend 
to the edge, while all the rest of the surface hears hairlike ribs parallel to 
the first and to the numher of five to six Ijetween each pair of secondary ribs. 
Observation . — I am not quite certain that the Leptcena described and 
figured by Schnur under the name of L. interstrialis, is identical with that 
which J. Phillips has described under the same name; hut not having at my 
disposal, just now, the material necessary to decide the question, I prefer not 
to speak definitely on the subject. 
Horizon and Localities . — If it he proved that Schnur’s determination 
is correct, this species is found l)oth in the Lower Devonian, at Daleiden, in 
theAIiddle Devonian of Blankenheim, of Gerolstein, and of many localities in 
Devonshire, also in the grey Deceptacidites Heptuni, Defr., shale of the 
Givet District. One specimen of it has been collected on the hanks of the 
Alurrumhidgee, near Yass, in a piece of reddish sandstone associated with 
indeterminable fragments of Fenestella, 
