. PARALLELODON FRAIPONTI. 165 



in some external characters. A new species, P. multilineatus, appears to me to 

 be undoubtedly the same shell as that previously described as Area Haimeana. 

 The description of the external ornament, which is stated in the remarks to be 

 peculiar to the species, is as follows (p. 144) : — " Surface ornee de quinze ou seize 

 plis concentriques assez larges et peu saillants, separes les uns des autres par un 

 etroit sillon, qui les fait paraitre imbriques ; chacun de ces plis porte cinq ou six 

 fines stries, peu perceptibles a la simple vue." 



The external shape of the shell seems to differ from that of the cast in 

 de Koninck's original figures and in my own. This is doubtless due to the over- 

 growth of the edges of the valves, and to their being in contact and obscuring the 

 typical Arciform shape that is so apparent in casts. 



Paeallelodon Fbaiponti, de Koninck, 1885. Plate XII, figs. 8, 10, and 13. 



Paeallelodon Fbaiponti, de Koninck. Annales Musee R. Hist. Nat. Beige, 



vol. xi, p. 146, pi. xxiv, figs. 3 and 

 24 ; pi. xxv, fig. 23. 



Specific Characters. — Shell of moderate size, evenly gibbose, transversely sub- 

 quadrate. The anterior end is short, convex in contour ; the narrowest part of 

 the valve in the dorso-ventral direction. The anterior border is semicircularly 

 curved, and passes below without break into the inferior border, which is very 

 gently convex downwards for the greater part of its extent, but curves upwards 

 behind to meet the posterior border at a very much rounded obtuse angle. The 

 posterior border is straight and obliquely truncate from above downwards and 

 backwards ; it is nearly twice as long as the anterior border, and joins the hinge- 

 line above at a well-marked obtuse angle. The hinge-line is straight, somewhat 

 shorter than the longest transverse diameter. The umbones are comparatively 

 large, obtusely rounded, incurved, and directed forwards, slightly elevated above 

 the hinge-line, non-contiguous, and situated in the anterior third of the cardinal 

 line. The valves are regularly swollen, convex in the anterior two-thirds of the 

 shell, the most gibbose portion being near the umbo. Behind a line passing 

 from the posterior border of the umbo to the posterior-inferior angle the valve is 

 rapidly compressed, so as to be hollow, but there is no angularity or ridge to mark 

 the change. The ligamental area is very narrow. 



Interior. — I have seen no specimen showing the muscle-scars, or the hinge- 

 plate. The pallial sinus is entire. Casts show several concentric, irregularly 

 placed grooves, which correspond to the deeper concentric lines on the exterior of 

 the shell. 



Exterior. — The surface appears almost smooth to the naked eye with an 

 occasional deep concentric line, but under the microscope the valve is seen to be 



