500 F. R. Coicper Reed — Fossils from Haverforduest . 



MODIOLOPSIS SUIJGRADATA, Sp. HOV. (PI, XXIV, FigS. 5, 6.) 



Description. — Shell subquadrate to transversely ovate, short, 

 oblique, widening posteriorly, about 1 J to \h times as long as high ; 

 greatest height at about two - thirds of its length. Hinge-line 

 straight, extending about two-thirds the length of the shell behind 

 the beaks. Anterior end of shell somewhat narrowed, subtrnncate, 

 rounded, about two-thirds the greatest height of the shell. Inferior 

 margin slightly convex, oblique, gently sinuated. Posterior end 

 broadly rounded, regularly convex ; inferior angle not produced. 

 Beaks situated at about one-third the length of the shell from 

 anterior extremity, small, obtuse, rising a little above hinge-line. 

 Surface of valves gently convex, with a more or less developed 

 rounded umbonal ridge traversing valve ; cardinal slope somewhat 

 flattened ; mesial depression faint or nearly obsolete, but always 

 indicated on inferior margin by sinuation of edge. Surface of shell 

 mai'ked with concentric striee and a few stronger growth-ridges, 

 meeting hinge-line at an angle between 75° and 90°. 



Dimensions. 



1. II. III. 



Length 10-5 ... 9-0 ... 14-o mm. 



Maximum height ... 8-0 ... 7"5 ... 10-0 mm. 



Horizon and Locality. — Slade Beds : roadside near St. Martin'u 

 Cemetery, Haverfordwest. 



Remarks. — The short, broad, subquadrate shape of this species, 

 especially emphasised in the younger and smaller specimens, recalls 

 both 31. gradafa, Salt.,' and M. quadrata, Salt.,' but the hinge-line is 

 longer and the inferior angle not produced as in the former, while 

 the latter has a less oblique shape, the inferior margin is not 

 sinuated, and the anterior end less narrowed. 



GoNiopHOKA cf. CYMB.aEF0RMis (Sow.). (PI. XXIV, FigS. 15, 15a.) 



There is a large Lamellibranch from the Slade Beds which bears 

 a great resemblance to GoniopJiorn cymhceformis (Sow.), but this 

 species typically belongs to a much higher horizon (i.e. Ludlow). Our 

 single Slade specimen, which measures 52 mm. in length, 23 mm. in 

 height,' and 29 mm. in depth, has the peculiar elongated form with 

 very deep valves, incurved anterior beaks, strong angular umbonal 

 ridge, pointed extremity, and large flattened cardinal region and 

 posterior side inclined at an angle of 45°-60° to the general convex 

 surface of the shell. The beaks are small, but acute, and have 

 a distinct cordate, slightly depressed lunule below them. Below the 

 umbonal ridge the valve is rounded and convex, and the shell is 

 marked with concentric stria? and rugjB, the latter being strongest 

 and most regular near the beaks and on the anterior part of the 

 umbonal ridge. The much flattened elongate cardinal slope is only 

 marked with fine concentric striae, the sudden change in the character 



1 Salter: Mem. Geol. Surv., vol. ii, pt. 1, p, 363, pi. xx, figs. 3-5. 



2 Ibid., p. 363, pi. XX, fig. 1. 



