LIMA. 37 



slmlloAV groove nuMitioiied in tlic description of Tj. plonfjafd) tliore is another row of 

 similar, but slightly smaller spines. In the furrows between the main ribs there 

 are transverse ridges. 



On account of the close resemblance in the form and ribbing of //. orhinaid 

 to L. olongntn, and also from the fact that \n some specimens of the former the 

 ornamentation of the ribs is absent from a part of the shell and the ribs are tlion 

 indistinguishable from those of L. cloiigatu, I am led to consider L. rchinata as not 

 more than a variety of L. elongafa. Further, in some specimens of L. doiigata the 

 summits of the ribs are serrate. 



L.rlonr/nta var. echinata pi^esents some resemblance to L.Schmeiswri, Wollemann,' 

 from the BJiotomagensis-'Pliinev of Liineburg. 



Ti/pes. — In the Sedgwick Museum, from Burwell. 



Diiifrihiifinu. — Totternhoe Stone {Tfdhi.^fi'v siihglohnftus zone) of Burwell and 

 Cherry Hinton. Also recorded in the ' Geological Survey Memoirs ' from the zone 

 of Schhriiliiichia cariaiis. 



Lima (Mantellum) rAXTATiRKUEXSis, nom. nov. Plate VI, figs. 10a, h, 11, 12. 



1881. Lima ornata. 7?. Ether'nhje. In Pcnnimj and Jukes-Browne, Geol. Cam- 

 bridge, p. 144, pi. iii, fig. 2 (lion 

 ornata, d'Orbigny, 1847 ; nr>ii 

 ornata, Buvignicr, 1852). 



Dpscriptinn. — Shell moderately convex, oval or rounded-oblong. Anterior 

 margin rounded. Uml)ones and ears not seen. 



Ornamentation consists of 16 or 17 main ribs with a few small ribs at the 

 posterior end. The anterior ril)s are sti'ong, roof-like, with ridged summits ; 

 posteriorly the ribs become less prominent and the interspaces less depressed. 

 Both ribs and grooves are ornamented with fine, well-developed ribs, which arc 

 closer together on the ribs than in the grooves ; usually three or four occur on 

 each side of a main rib and three in each erroove. iSTumerous concentric rids:es 

 occur and give rise to spiny projections where they cross the fine radial ribs. 



Affinitipn. — In form this appears to be similar to L. pamllehi (p. 28), but has 

 fewer ribs and is much more highly ornamented. The small rib at the bottom of 

 the groove is not distinguishable from the other ribs. 



It is more convex, has fewer ribs, and has the fine ornamentation better developed 

 than in L. intermedia. 



Iii-Diarh. — This species is known b}' three specimens only. All arc imperfect 

 near the umbo, but the fine ornamentation is well-preserved. 



' Abhandl. d. k. proussiscli. geol. Landesanst., N. F.,' Heft 37 (1902), p. 5.1, pi. vii, fig. 9. 



