4 CRETACEOUS LAMELLIBRANCHIA. 



summits, separated by broader rounded furrows. Both ridges and furrows bear 



numerous flattened radial ridges separated by linear grooves ; the ridges, in 

 well-preserved specimens, are serrate or granular. At distant intervals a few 

 well-marked growth-ridges occur. 

 Measurements : 



(i) (2) 



Length 49 . 70 mm. 



Height 54 . 78 



(1, 2) Upper Greensand, Devizes. 



Affinities. This species is distinguished from L. canalifera (p. 1) by the 

 valves being more compressed, the ribs fewer in number, the grooves relatively 

 broader, and by the presence of fine radial ornamentation on the ribs and grooves. 



Remarks. This appears to be a rare species in England. The specimens from 

 Devizes are in the Museum of Practical Geology. The specimen from Humble 

 Rocks was collected by Mr. Jukes-Browne, and is now in the Sedgwick Museum. 



Type. From the Cenomanian of Coudrecieux, Sarthe. 



Distribution. Upper Greensand (zone of Schlccnbachia rostrata) of Devizes. 

 Base of Chalk Marl (Bed 10) of Humble Rocks, West of Lyme Regis. 



LIMA VECTENSIS, sp. nov. Plate II, figs. 2, a c. 



Description. Shell large, rather compressed, ovate, height greater than length ; 

 antero-dorsal margin straight, the remainder forming a regular curve. Anterior 

 area deeply depressed. Apical angle apparently about 100. Anterior ear small ; 

 posterior ear larger, with a few ribs. 



Ornamentation consists of about 40 rather strong, narrow ribs, with rounded 

 summits which, in places, are slightly tubercular. The ribs are closer together on 

 the anterior part of the valves than elsewhere. The interspaces are much broader 

 than the ribs, and are flat or slightly concave ; they are marked by numerous fine, 

 concentric ridges. 



Affinities. This species resembles Lima Dujardini, Deshayes, 1 from the 

 Senonian, but the interspaces are flat or nearly flat instead of concave, and the 

 well-marked scale-like projections which, in L. Dujardini, are placed at intervals 

 on the ribs, but without a concentric arrangement, are not seen. 



1 Dujardin, 'Mem. Soc. geol. de France,' vol. ii (1837), p. 227, pi. xvi, fig. 3. D'Orbigny, 'Terr. 

 Cret.,' vol. iii (1847), p. 569, pi. ccccxxvii, figs. I 4>. 



