F. R. Coioper Reed — Fossils from Haverfordwest. 449 



Eemakks. — In typical examples of 0. porcata,^ as well as ia 

 the type-specimen, the pedicle valve is flattened, and only convex 

 about the beak and on the lateral portions ; there is also a moderate 

 depression down the middle of the valve, and the muscular area is 

 remarkably square. In none of these points does our variety agree 

 with it. The ornamentation of the surface varies much in the 

 species, but ours is not in complete agreement with any figured, 

 though not much stress need be laid on this fact. This new variety 

 may be named sladensis. 



Orthis afif. BoucHARDi, Dav. (PI. XXIII, Figs. 8, 9.) 

 Description. — Shell subquadrate, rounded, a little wider than 

 long, plano-convex ; hinge-line straight, a little less than the 

 greatest width. Pedicle valve convex, slightly keeled, rounded ; 

 beak high, incurved; hinge-area triangular, large, vertical or steeply 

 inclined. Brachial valve flattened, with deep, broad median sinus 

 of nearly uniform width, deeply sinuating anterior margin ; small 

 inconspicuous beak ; narrow hinge-area. Interior of pedicle valve 

 with small teeth, and faint muscular impressions. Interior of 

 brachial valve with bilobed cardinal process ; stout strong crura ; 

 two pairs of adductor impressions, distinct, rather wide apart, with 

 low rounded ridge between them, anterior pair elongated oval, 

 twice as long as posterior pair, which are subcircular. Surface of 

 valves ornamented with about 30 to 40 subangular ribs, mostly 

 simple, but some bifurcating, and with a shorter one intercalated 

 between each pair ; usually finely imbricated concentrically. 

 Dimensions. 



Length 6'Orain. 



Width at hinge ... 7'Omni. 



Localities and Horizons. — Eedhill Beds, Prendergast Place ; 

 Slade Beds, near St. Martin's Cemetery, Haverfordwest. 



Remarks. — This small species appears to be allied to or perhaps 

 a variety of the Wen lock species 0. Bouehardi, Dav,,'^ but the ribs 

 in the latter are fewer and the imbrications coarser. 



Strophomena (?) MEDiocosTALis, sp. nov. (PI. XXIII, Figs. 10, 



10a, 11.) 



Description. — Shell transversely semi-elliptical, about 1^ times 

 to twice as wide as long ; cardinal angles acute, more or less alate ; 

 hinge-line straight, at greatest width of shell ; lateral and anterior 

 margins rounded ; concavo-convex, more or less flattened ; valves 

 close together. Pedicle valve gently convex, slightly bent down 

 near anterior and lateral margins, flattened towards hinge-line ; beak 

 small, acute, not prominent nor rising above hinge-line ; hinge-area 

 narrow, triangular, steeply inclined. Brachial valve flattened or 

 slightly concave ; beak small, not prominent ; hinge-area very 

 narrow. 



Interior of pedicle valve with pair of small, divergent, triangular 

 diductor impressions extending about one-fourth the length of the 



^ Davidson: op. cit., p. 250, pi. xxxi, figs. 12-20 ; pi. xlvi, fig. 4. 

 2 Davidson: op. cit., vol. iii, p. 209, pi. xxvi, figs. 16-23. 



DECADE V. — VOL. II. — NO. X. 29 



