MODIOLA RADIATA. 13] 



in the interspaces between certain pairs. These lines are often closely imbricate, 

 and here and there are crossed by obscure concentric sulci. 



On the ears concentric markings are stronger, faint radiating lines being seen 

 on the anterior ear only. 



Dimensions. — Text-fig. 1, p. 130, a left valve, measures: — 



Antero-posteriorly . . . .30 mm. 



Dorso-ventrally . . . .30 mm. 



Locality. — Shale beneath massive limestone, Criobin, Pembrokeshire. 



Observations. — The specimen on which the description is based belongs to 

 Dr. Vaughan. It is a left valve in fairly perfect condition, but I doubt if the 

 whole of the posterior ear is exposed. I refer the specimen to A. constans 

 (de Koninck), a shell occurring at Panquys, stage II. From the general character 

 of the shell I think it belongs to the group represented by Avicuhpecten stellaris, 

 Phill., sp., the ears of which have similar characters. 



Modiola radiata, de Koninck, 1885. Plate XXII, figs. 13 — 10. 



Caediomoepha badiata, de Koninck, 1842. Descr. Anini. Foss. Terr. Carb. Belg., 



p. 109, pi. ii, fig. 6 ; pi. iii, fig. 9. 



Cypricardia oblonga, M'Coy, 1844. Synops. Carb. Foss. Ireland, p. 60, pi. viii, 



fig. 21. 



Mytilus Koninckianus, de Ryckholt, 1853. Melanges Paleontol., pt. ii, p. 89. 



Modiola badiata, de Koninck, 1885. Ann. Mus. Boy. d'Hist. Nat. Belg., torn, xi, 



p. 176, p. xli, figs. 42, 43. 



Specific Characters. — Shell of medium size, transversely suboval, obliquely 

 gibbose, very convex and expanded. The anterior end very short, its border 

 rounded. The inferior margin slightly sinuous, with a well-marked byssal opening 

 about the junction of the anterior and middle thirds of its length. The posterior 

 border straight for the greater part of its extent, very oblique, bluntly rounded 

 below, but making a large obtuse angle above with the hinge-line. The latter is 

 straight, much shorter than the antero-posterior diameter of the valves. The 

 umbones are much swollen, pointed, incurved and twisted forwards, contiguous and 

 almost terminal. The dorsal slope is broad and compressed, often hollow. No 

 escutcheon or lunule. 



Interior. — The adductor muscle-scars are normal in position. Ligament 

 internal. Surface smooth, with some broad, obscure, concentric, undulations 

 jriorly. 



Exterior. — The surface in the young shell is almost smooth; but in adults well- 



