448 F. R. Cowper Reed — Fossils from Haverfordwest. 



valve of a subcircular, conical shape, with a non-central elevated 

 umbo situated at about one-third the diameter from the posterior 

 edge. The surface is ornamented with about fifty strong radiating 

 ribs, equidistant, of equal strength, and projecting a little beyond 

 the mai'gin of the shell, with 2-3 much finer shorter ones between. 

 Dimensions. 



Diameter 4*0mm. 



Height I'Smm. 



Locality. — Koadside near St. Martin's Cemetery, Haverfordwest. 



Horizon. — Slade Beds. 



Eebiarks. — C. Grayi is, according to Davidson, only found in the 

 Wenlock Limestone. The American Ordovician species G. Lcelia, 

 Hall,^ from the Utica and Lorraine groups appears to be allied to 

 the Slade species. 



Orthis (Plesiomys) poroata, McCoy, var. nov. sladensis. 

 (PI. XXIII, Figs. 4-7.) 

 This species was recorded with a query by Messrs. Marr & 

 Koberts from the Slade Beds. Many fine specimens of a variety of 

 it are included in Mr. TurnbuU's collection. The variety is distinct, 

 particularly with regard to its internal characters, and may have to 

 be regarded as specifically different to the typical 0. jyorcata. 



Description. — Shell biconvex, semi-elliptical, wider than long, 

 broadest at about half its length ; hinge-line straight, less than 

 greatest width of shell ; cardinal extremities obtusely angular, sides 

 and front rounded. Pedicle valve moderately convex, less so than 

 brachial valve ; no medial depression ; beak moderate, slightly 

 incurved, not prominent, but rising a little above hinge-line ; hinge- 

 area triangular, not very wide, inclined. Brachial valve slightly 

 more convex than opposite valve ; beak rather smaller, slightly 

 incurved ; area triangular, nearly vertical, of approximately the 

 same size. Interior of pedicle valve with small, elongated-suboval, 

 muscular area, definitely circumscribed, acutely indented in front, 

 about one-fifth the length of the valve ; teeth large. Brachial valve 

 with oval cardinal process ; low rounded median ridge running 

 forwards for about one-fourth the length of the valve between deep, 

 narrow, elongated muscular scars ; crura stout. Surface of valves 

 covered with numerous subequal fine rounded ribs, slightly curved 

 on lateral portions of shell, increasing by bifurcation at about 

 one-fourth their length, and frequently again nearer margin, to about 

 150-160 round margin. A few strong concentric growth ridges 

 generally present, and a fine concentric striation. 

 Dimensions. 



I. II. 



Length 22*5mm. ... 25-Omm. 



Width at hinge -line 22*0mm. ... 27-Omm. 



Maximum width 28-5mm. ... 36-Omm. 



Locality. — Koadside near St. Martin's Cemetery, Haverfordwest. 

 Horizon. — Slade Beds. 



1 Hall & Clarke: Palceont. New York, vol. viii, Brach., pt. 1, 1892, pi. ivH, fig. 1. 



