94 DEVONIAN FAUNA. 



1885. ScnizoDUs aupressits, Hall. Pal. N. T., vol. v, pt. 1, No. 2, p. 449, 



pi. Ixxv, figs. 3 — 9. 

 ? 1885. — RHOMBEUS, Hall Ibid., p. 452, pi. Ixxv, figs. 19—23. 



1885, — Chemungensis, Hall. Ibid., p. 453, pi. Ixxv, figs. 31—34, 36— 



41, 45. 

 1885. — iEQUALis, Hall. Ibid., p. 458, pi. Ixxv, fig. 35; and pi. xcv, 



fig. 29. 

 1893. Ctpeicabdia deltoidea, Collins. Tran3. Eoy. Geol. Soc. Cornwall, vol. 



xi, p. 36. 

 1893. ScHizoDUS DELTOiDEtrs, ColUnst. Ibid., p. 38. 



Description. — Shell moderate in size, convex, slightly transverse, subquadrate. 

 Umbo small, direct, incurved, slightly truncate behind, and situate rather in front 

 of the centre. Hinge-margin short, convex. Hinge containing a large, triangular 

 central tooth, and a smaller, more elongate, and indistinct posterior tooth. 

 Anterior margin broad and roundly convex. Inferior margin rather long, slightly 

 convex. Postero-inferior corner rather produced and subangular. Posterior 

 margin oblique and slightly convex. Contour of back divided by a blunt angle 

 running from the umbo to the postero-inferior point, in front of which it is trans- 

 versely flat, becoming convex in front, and behind which it is oblique and flat. 

 Posterior muscle-scar high up near the centre of the posterior hinge-margin. 



8iz6. — Height 16 mm., length 20 mm., depth of one valve 5 mm. 



Localities. — In the Museum of Practical Geology are two specimens from 

 Marwood, six from Shirwell, one from Petherwyn, and one from West Angle 

 Bay, Pembrokeshire. In the Porter Collection is one from Marwood ; in the 

 Woodwardian one from Marwood and two very obscure specimens from Baggy 

 Point. 



BemarJcs. — The Petherwyn specimen almost exactly agrees with Phillips's 

 figure, the only difference being that it is perhaps slightly more transverse. 

 Being in the Museum which contains so many of his figured specimens, it is 

 probable that it is the original type of his Cypricardia deltoidea, and it is to be 

 observed that Phillips noted its resemblance to Axinus. 



M'Coy states it to be not uncommon in the sandstones of Baggy Point, and it 

 seems probable that thebeds to which he refers are those which have contributed eight 

 specimens from Shirwell and Marwood to the same museum. The first question, 

 therefore, is whether these specimens can be identified with the type. They diSer at 

 first sight in being flatter and in having a less prominent umbo, above which the 

 hinge is seen, whereas it is invisible in the type specimen. At this point Mr. 

 Porter's specimen may be noted as uniting them in shape, and partially showing the 

 teeth. These Marwood specimens are, indeed, of all shapes, long and high, but this 

 is probably largely due to fossilisation, or at least to similar causes to that which 

 produced such variations in the specimens of Cucullwa and Avicula of the same 



