LIMA. 



11 



right angle. Umbones of moderate size. Area large, with a large triangular 

 ligament pit near the middle but bending posteriorly. Anterior area large, deeply 

 depressed, especially near the ears. Ears rather large, the anterior triangular, the 

 posterior rather larger, more elongate ; surface with growth-lamellae only. 



Surface ornamented with numerous (43 to 52) radial ribs, which arc straight or 

 slightly undulating. The ribs are flattened ; near the umbo they are separated by 

 narrow grooves, but in passing ventrally the grooves increase in width and become 

 as wide as or wider than the ribs. The grooves are rather shallow and rounded. 

 The anterior and posterior ribs are narrower than the others. Near the umbo the 

 grooves are punctate, but in passing ventrally the pits soon become replaced by 



Fia. 2. — Lima (Plagiosti 



i) subrigida, Rdrner. Claxby Ironstone, Benniworth Haven. Bight valve. 

 Natural size. Sedgwick Museum. 



transverse furrows separated by ridges, and the latter may pass on to the ribs. On 

 the anterior area ribs are small or absent, but growth-lines are usually distinct. 



Measurements : 





(i) 



(2) 



(3) 



(4) 



(5) 



(6) 



(?) 



(8) 



(9) 



Length 



109 



100 



80 



73 



72 



04 



63 



38 



31 mm 



Height 



114 



108 



85 



79 



76 



65 



65 



36 



40 „ 



Thickness 



— 



03 



— 



— 



— 



— 



36 



— 



55 



Number of ribs 



48 



49 



48 



51 



46 



43 



52 



52 



44 



(1—9) Claxby Ironstone, Benniworth Haven. 



Affinities. — L. vignevlensis, Pictet and Campiche, 1 is distinguished from 

 L. subrigida by its more quadrilateral outline, more numerous ribs and finer 

 1 'Terr. Cix ; t. Ste. Croix' (1869), p. 138, pi. clxii, tigs. 5—8. 



