146 F. R. Cowper Reed — Salter s Undescribed Species. - 



a series of undulating, equidistant, regular, transverse, coarse 

 striae, six in a space of 4 mm. These striae on the cast would be 

 represented on the surface of the shell by raised thread-like lines. 

 But this material is absolutely insufficient for the creation of a new 

 species, and Blake (loc. cit.) hesitates in identifying it with 

 0. recticinctum, partly on the ground of its imperfect preservation 

 and partly because it comes from a different geological horizon. 

 It seems advisable, therefore, to let the name drop, as the original 

 specimen does not admit of a sound species being established. 



LAMELLIBEANCHIATA. 



Pteeinea exasperata, Salter. (PI. VII, Figs. 3-5.) 



1873. Pterinea exasperata, Salter: Cat. Camb. Sil. Foss. Woodw. Mus., p. 150 



(« 813, a 814, a 815, a 816). 

 1891. Fterincea exasperata, "Woods : Cat. Type Foss. Woodw. Mus., p. 89. 



The specimens labelled Pterinea exasperata by Salter are eleven 

 in number. All are from the Wenlock Limestone of Dudley and 

 belong to the Fletcher Collection. One has both valves preserved, 

 though the right one is somewhat imperfect. The others are all 

 left valves, and one (a 815) shows the inner side of this valve. Five 

 more specimens of this species have been acquired since 1873. 

 Salter (loc. cit.) described it as " a reticulate species, long known 

 but not yet described." 



Diagnosis. — Body of shell obliquely ovate, elongate, unequally 

 biconvex ; long straight hinge-line ; left valve slightly more convex 

 than the right; furnished with small rounded, triangular anterior 

 ear and large flattened posterior wing. 



Left valve with obliquely elongate convex body ; beak gibbous, 

 prominent ; anterior ear not sharply marked off from body ; posterior 

 wing large, pointed, more than two-thirds the length of posterior 

 slope, depressed, flattened, more or less distinctly marked off from 

 body, posterior margin concave. Hinge-line long, straight, making 

 angle of about 30°-40° with body behind umbo. 



Surface of body marked by strong, straight, radiating, narrow, 

 equidistant ribs, 25 to 35 in number, very feebly developed or 

 absent on anterior and posterior ears. Half-way between each pair 

 of these main ribs is a finer, thread-like I'ib which begins at some 

 distance from the beak, and increases in strength towards the margin 

 so as ultimately to be equal in size to the main ribs. Eibs crossed 

 by regular, equidistant, concentric, scale - like lamellae, arched 

 backwards towards the umbo between each pair of main ribs, and 

 between every pair of ribs near the ventral margin. The lamellse 

 are continued on to the ears, where they are more closely packed 

 together and crenulated, and on the posterior ear are parallel to the 

 concave posterior margin. Right valve rather less convex than left 

 valve, but in other respects apparently similar. 



Measurements. I. 



mm. 

 Length along oblique axis of body ... 30 



Length at posterior end ... ... ... 21 



"Width along hinge -line 24 



