PARALLELODON. 113 



It closely resembles P. pygmseus, Whiteaves, which seems to be equally 

 variable in shape, but it is still smaller, being only about 4 mm. instead of 10 mm. 

 in length. Whiteaves compares his shell with Macrodon parvus, White and 

 Whitfield. 1 



Affinities. — Our species approaches Macrodon Hamiltonise, Hall, 2 in shape, but 

 is a minute instead of being a rather large shell. 



Macrodus venustus, Stein., 3 as given by Beushausen,* seems much the same 

 shape, but is very much larger and apparently more trigonal. 



2. Parallelodon peisods, Goldfuss, sp. ? Plate XII, fig. 6. 



1834-40. Aeca peisca, Goldfuss. Petref. Germ., vol. ii, p. 283, pi. clx, fig. 10. 



Description. — Left valve rather small, slightly oblique, very convex, very 

 transverse. Hinge-line as long as the shell, broad behind, where it has several 

 long thin linear horizontal teeth. Umbo very prominent, incurved, tending 

 forward and situated at or about the anterior fourth of the length. Anterior margin 

 broad, slightly convex and oblique, meeting the hinge-line at a somewhat acute 

 angle. Inferior margin very long, nearly straight and direct. Postero-inferior 

 corner slightly produced, rounded. Posterior margin slightly convex and oblique, 

 meeting the hinge at a slightly obtuse angle. Contour of back vertically very 

 convex, horizontally flattened but becoming concave in the supero -lateral parts ; 

 with an obtuse ridge or angle running from the umbo to the postero-inferior corner, 

 before which there seems to be a slight dorsal compression. Surface with strong 

 concentric growth-ridges ; finer ornament unknown. 



Size. — Height 8 mm,, length 17 mm., depth of one valve 3 mm. 



Locality. — One specimen is in my Collection from Ironpost, near Dulverton. 



Remarks. — The only specimen of this shell being a cast with very slight 

 indications of the ornament, it is impossible fully to identify it. All that can be 

 said is that it seems to be exactly like the equally imperfect specimen described by 

 Goldfuss. 



Affinities. — Area MicJielini, d'Archiac and cle Verneuil, 5 appears to have a 

 straighter, less oblique front margin, and a stronger dorsal constriction. 



1 1862, White and "Whitfield, ' Proc. Boston Soc. Nat. Hist.,' vol. viii, p. 299 (Lower Carb.). 



2 1885, Hall, ' Pal. N. T.,' vol. v, pt. 2, p. 349, pi. Ii, figs. 1—7, 10, 11. 

 » 1853, Steininger, ' Geol. Besch. Eifel,' p. 49, pi. ii, fig. 7. 



4 1895, Beushausen, ' Abhandl. k. Preuss. Geol. Landes.,' n. f., pt. 17, p. 39, pi. iv, figs. 3, 1. 



5 1842, de Archiac and de Verneuil, ' Geol. Trans.,' ser. 2, vol. vi, pt. 2, p. 373, pi. xxxvi, fig. 6. 



P 



