R. Etheridge, Jun. — Contrihiitions to Palceontologt/. 347. 



Scotcli Carboniferous beds, and have never yet succeeded in finding 

 any trace of an esternal ligament ; but, on tlie contrary, in a few 

 well-preserved interiors of the ty^Q species of Nucida, N. gihbosa, 

 Fleming (N. tumicla, Phil.), I have distinctly seen the cartilage-pit. 



As one of those intermediate forms which in esternal characters 

 unite the genera Leda and JVucula, the following undescribed species 

 is of some interest. I liave as yet only noted it from Scotch locali- 

 ties, and, although abundant as regards individuals, is one of the less 

 ■common species. 



Leda intermedia, sp. nov,, PL XIL, Fig. 3. 



Sp. chars. — Shell transversly elongate ; valves compressed and 

 flattened, least so below the beaks ; anterior side rounded ; posterior 

 side compressed, narrower than the anterior, with a blunt rounded 

 termination ; beaks nearly central, contiguous, depressed ; dorsal 

 outline slightly convex on the anterior side, concave and inclined 

 downwards on the posterior side ; ventral margin convex, most so on 

 the anterior side, inclioed upwards on the posterior side ; surface 

 with very close regular concentric stride. 



This is a well-marked shell, easily distinguishable from an allied 

 form, Z. attenuata, Fleming, by its very compressed valves, much 

 shorter posterior side, and the almost median position of the beaks, 

 Of all the published descriptions of Carboniferous Ledce within my 

 reach, L. intermedia approaches nearest to L. (Yoldia?) Icevistriata, 

 Meek and Worthen, from the upper part of the St. Louis Group of 

 the Carboniferous Limestone Series of Illinois.' 



Locality. — Orchard Quarry, about four miles south of Grlasgow, 

 in the shale of the Orchard Cement Stone (Upper Limestone Series). 

 Leda intermedia ranges from the Wardie Shales (Calciferous Sand- 

 stone Series) to the Upper Limestone Series. I have lately detected 

 it in the latter at Spy Mill, Water of Leith, near Edinburgh, 



EXPLANATION OF PLATE XII.^ 



Fig. 1. — Fteronites fluctuosus, EtTiexidge, from shale below the Main Limestone 

 (Lower Limestone Series), Cleekhimin Quarry, S.E. of Carluke. Collec- 

 tion of the Geological Survey of Scotland. x 1\. 



Fig. 2. — Avieulopecten ornatus, R. Etheridge, from shale of the Lower Limestone 

 Series, Kinghom, Fife. Natural size. Cabinet of Mr. D. J. Brown, 

 Edinburgh. 



Fig. 3. — Leda intermedia, R. Etheridge, from shale of the Orchard Cement Stone, 

 Orchard Quarry, near Glasgow. x 2. 



Fig. 4. — Portion of shell of another specimen, showing the close fine concentric strise. 



Fig. 5. — Conocardium decussatum, R. Etheridge, from the shale of the Orchard 

 Cement Stone. 



Fig. 6. — Fteronites regularis. R. Etheridge, from shale of the Upper Limestone 

 Series, Linn Spout, Dairy, Ayrshii-e. Cabinet of Mr. J. Young, Glasgow. 



Fig. 7« — Myacites ? {Allorisma) temdlineata, R. Etheridge, from Lower Limestone 

 Series at Cousland, near Edinburgh. Cabinet of Mr. D. J. Brown, 

 Edinburgh. 



1 Pall. 111. vol. 2, p. 282, pi. 20, f . 7, 



2 In consequence of the serious illness of the artist, Mr. C. L. Griesbach, this Plate 

 is unavoidably postponed until the September Niimber. — Edit. Geol. Mag. 



