1855.] BAILY SOUTH AFRICAN FOSSILS. 461 



carinata, carina elevata, longitudinaliter concentriceque striata ; 

 umbonibus approximatis ; area ligamenti angustata. 



Length, 2 inches -^ths. 

 Breadth, 2 inches j^ths. 



Shell gibbous, obliquely triangular, very abruptly truncate and 

 carinate. The keel is elevated, and is the highest part of the shell ; 

 umbos approximating ; hinge-area narrow. 



The two valves of this fine large Area, which are still united, 

 have a reticulated appearance, caused by the radiating lines being 

 crossed by transverse furrows of growth. 



It is allied to Area fibrosa, from the Greensand of Blackdown ; also 

 to A. Trinchinopolitensis, Forbes. 



Locality. — Cliffs on S. African coast, near the Umtafuna and Um- 

 zambani Rivers. 



Arca Natalensis, nov. sp. PI. XIII. fig. 2. 



A. testa subinflata, carinata, transverse ovata, antice oblique truncata, 

 angulata, postice rotundata; lateribus striatis, in medio sulcato- 

 striatis ; area cardinali lata, 4-striata ; umbonibus distantibus. 



Length, 1 inch ^ths. 

 Breadth, 1 inch j^th. 



Shell somewhat inflated, carinated, transversely ovate ; anterior 

 side obliquely truncated, and angular ; longitudinally sulcated ; car- 

 dinal area large, with four striations ; umbos distant. 



This description is founded on a single valve, in beautiful pre- 

 servation, and showing the interior and hinge-area. The strongly 

 ridged exterior and difference of form sufficiently distinguish it from 

 the last species. It closely resembles A. Japetica, from Pondicherry. 



There is also another species of Arca, too imperfect to determine. 



Locality. — Cliffs of S. African coast, near the Umtafuna and Um- 

 zambani Rivers. 



Genus Trigonia, Bruguiere. 



Trigonia elegans, nov. sp. PI. XIII. fig. 3. 



T. testa ovato-trigona, antice rotundata, postice producta et rostrata ; 

 costis arcuatis, oblique crenulato-rugosis, umbonibus obtusis sub- 

 recurvis ; area longitudinaliter sulcata, transversim costata ; carinis 

 marginali et interna depressis. 



Length ^^ths of an inch. 

 Breadth ^ths of an inch. 



1 



Shell ovately trigonal, moderately convex ; anterior extremity 

 rounded ; posterior extremity produced and rostrated ; ribs some- 

 what arched and crenulated obliquely ; umbos obtuse, slightly 

 recurved ; area longitudinally sulcated and transversely striated ; 

 striations of inner carina less numerous and more distinct ; carina 

 depressed. 



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