128 CARBONIFEROUS LAMELLIBRANCHIATA. 



Pterinopeoten pustulosus, sp. nov. Plate XXV, fig. 24. 



Specif c Characters. — Shell of medium size, quadrato-orbicular. The left valve 

 moderately gibbose. The anterior margin sinuous above, convex below. The 

 lower margin regularly convex, the posterior convex below, concave above. The 

 hinge-line straight, prolonged along the upper margin of both ears. The umbones 

 small, pointed, slightly raised, placed a little in front of the middle of the hinge- 

 line. The anterior ear of the left valve is large and compressed, not pointed in 

 front, its lower margin denoted by a broad space without radiating ribs, below 

 and above which the ribs are closer together. The postero-superior angle of the 

 shell large, compressed above and below with a more convex portion between. 



Interior. — Unknown. 



Exterior. — The surface of the left valve is ornamented with distinct thick 

 radiating, elevated ribs, which are studded with moniliform enlargements becoming 

 apparent some little distance from the umbo. Between each pair of thick nodulose 

 ribs is a thin linear rib, which becomes sinuous or slightly moniliform near the 

 lower margin. Between the ribs the surface of the shell is crossed by fine 

 equidistant, concentric lines, best marked in the umbonal region. There are three 

 radiating moniliform ribs on the anterior ear, and fine concentric lines of growth. 

 The ornament of the postero-superior portion of the valve resembles that of the 

 surface of the valve. 



Dimensions. — PI. XXV, fig. 24, measures — 



Antero-posteriorly . . . .75 mm. 



Dorso-ventrally . .70 mm. 



Convexity of left valve . . .10 mm. 



Localities. — The Carboniferous Limestone of Kniveton and Gluttondale, Derby- 

 shire. 



Observations. — This species is founded on two specimens from the upper beds of 

 the Carboniferous Limestone of Derbyshire, both in my collection. The very 

 distinct ornament and arrangement of ribs and more quadrate form distinguish 

 this species from others having moniliform ribs, as P. eximius and P. granosus. In 

 these the ribs are much finer and more numerous. I have not yet seen the right 

 valve. The ornament resembles closely that of Amculopecten Murchisoni, affording 

 a good example of homoeomorphy in two different genera. 



Pterinopeoten carbonarius, sp. nov. Plate XXV, figs. 14 — 16. 



Specific Characters. — Shell small, quadrato-subcircular, the left valve moderately 

 convex, the right valve flattened. The anterior border curved, the inferior con- 



