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DEVONIAN FAUNA. 



6. Actinopteeia Justi, Freeh, sp. PL VII, figs. 12, 12 a ; and PI. VIII, fig. 1. 



1891. Avicula Justi, Freeh. Abhandl. Geol. Specialk. Preuss., Band ix, pt. 3, 



p. 36, pi. iii, fig. 11 ; and pi. xiv, fig. 7. 



Description. — Left valve of moderate size, quadrate, nearly as broad as long. 

 Umbo prominent, slightly oblique, incurved, slightly elevated above the hinge- 

 line, and situated nearly at its anterior end. Hinge-line straight and equal to 

 the length of the shell. Anterior wing small, convex, defined, and bearing three 

 or four ribs. Anterior margin broad, nearly erect. Inferior margin moderately 

 convex, hardly oblique. Infero-posterior corner broadly rounded. Posterior 

 margin erect and nearly straight. External contour evenly convex in the centre, 

 almost perpendicular in front, and sloping gently to the other margins. Hind 

 wing large, sloping, and undefined. Surface bearing about thirty large, rounded, 

 distant ribs, of which about ten are on the hind wing ; the whole being crossed 

 by coarse striae and by a few indistinct undulations. Shell-structure thin. 



Size of left valve. — Length 30 mm., breadth 26 mm., depth 9 mm. 



Localitij. — A single specimen from Wolborough is in Mr. Vicary's Collection, 

 and two smaller examples from Lummaton are in my Collection. 



Remarks. — Mr. Vicary's specimen is almost perfect in shape, but, if not 

 actually a cast, it is certainly without the outer layer of shell, and hence its 

 ornament is lower and more confluent than would otherwise be the case. 



The species is distinguished from those that accompany it by its quadrate 

 shape, its broad and erect anterior side, and the fewness and coarseness of its 

 ribs. It appears to agree accurately with the German fossil to which Freeh has 

 given the name Avicula Justi. 



The anterior wing in Mr. Vicary's specimen is very obscure, but I think the 

 figure at PI. VIII, fig. 1, would have more accurately represented it if a minute 

 triangular slip had been removed from its upper part. 



A ffinities. — A. placida differs in the much greater size of its front wing, and 

 the fineness and closeness of its markings. 



A. dilatata is much more transverse and has finer and more numerous ribs. 



Whether A. Justi is more than a variety of A. Wurmii may perhaps be ques- 

 tioned. Our English material would be hardly sufficient by itself to decide the 

 point. But a comparison of our specimens of the two forms with Freeh's 

 description of them confirms the view that they are distinct species. Not only 

 are the ribs much fewer and coarser in A. Justi, but the anterior side is broader 

 and less truncated, so that the shell is squarer in shape. 



