PROTOCARDIA. 197 



from Haklon, which resemble in shape the higher forms of P. sphaeroidea, but the 

 umbones are narrower and more curved, and the carina is more distinct. 

 Better specimens are needed before a satisfactory comparison can be made. The 

 occurrence of P. sphaeroidea in the Upper Greensand (zone of Pecten asper) of 

 Wiltshire has been recorded by Mr. Jukes-Browne. 



Protocardia, sp. Plate XXXI, fig. 5 a, b. 



Description. — Shell globose, with rounded outline, slightly inequilateral, height 

 and length nearly equal. Umbones low, curved anteriorly. The posterior 

 part of the shell (except near the postero-dorsal margin) is ornamented with from 

 ten to twelve strong radial ribs ; the remainder of the shell bears numerous, small 

 concentric ribs. 



Affinities. — This species resembles P. peregrinorsa (d'Orbigny), 1 but the area 

 with radial ribs is relatively larger, and the concentric ribs are finer. 



Remarks. — The only specimens seen are two in the Museum of Practical 

 Geology and two in Mr. Lamplugh's collection. 



Distribution. — Speeton Clay (zone of Belemnites lateralis, D, 4) of Speeton. 2 



Protocardia Hillana (Soiverby), 1813. Plate XXXI, figs. 6 a—c ; Plate XXXII, 



fig. 1—6. 



1813. Cardium Hillanum, /. Sowerby. Min. Conch., vol. i, p. 41, pi. xiv 



(upper figure). 

 181D. — ■ — Lamarck. Hist. nat. Anim. sans Vert., vol. vi, p. 20. 



1837. A. Ooldfuss. Petref. Germ., vol. ii, p. 220, pi. cxliv, 



fig. 4. 

 F. Dujardln. Mem. Soc. geol. de France, vol ii 

 p. 224. 



1840. H. B. Geinltz. Char. d. Schicht. u. Petref. des 



siichs. Kreidegeb., pt. 2, p. 53. 



1841. F. A. Burner. Die Verstein. d. nord-deutsch. 



Kreidegeb., p. 71. 



1842. Requenianum, P. Matheron. Catal. Foss. du Depart, des 



Bouches-du- Rhone, p. 157, 

 pi. xviii, fig. 6. 



1 'Pal. Franc. Terr. Cret.,' vol. iii (1844), p. 16, pi. ccxxxix, figs. 1 — 3; Pictet and Campiche, 

 ' Terr. Cret. Ste. Croix ' (' Mater. Pal. Suisse,' ser. 4, 1866), p. 254, pi. cxxi, figs. 1, 2. 



2 Internal casts of a globose and nearly equilateral " Cardium" (perhaps Protocardia), from the 

 Spilsby Sandstone of Donnington, are in the Sedgwick Museum. 



26 



