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PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



It is of small and very medium size when compared with the more 

 adult forms from Queensland, which sometimes reach 9 inches in 

 length ; the valves are well inflated and covered with wide and 

 rounded growth bands bearing intervening concentric striations ; the 

 posterior region is subangulate and furnished with strongly oblique 

 lines of growth, whereas anteriorly the valves are slightly compressed 

 and narrow in the direction of the outer margin ; the luuular excavation 

 appears to be rather shallower than usual, probably on account of the 

 absence of the umbones. 



Dimensions {approximate). — Length 60, height 50, diameter 35 mm. 



FiSSILUNULA CLARKEI (Moore). 

 A = Left lateral view of specimen. 



B = Ventral aspect of same, showing well-inflated valves. 

 hoc. White Cliffs. British Museum (Geol. Dept., L. 21274). 



Moore's original description of the Queensland shell was based upon 

 very imperfect material, but from the later studies of Mr. Etheridge, 

 jun., of better preserved examples the real affinities of the species 

 came to be more accurately known. From a delineation of the 

 hinge-chai'acters and other important internal structures, that author 

 was able to prove fairly close relationships to Isocardia^ and thus he 

 made the species tlie type of his new genus Fissilimula. The present 

 fossil compares favourably with a partially testiferous cast originally 

 collected by Mr. H. Y. L. Brown from the Cretaceous region north of 

 Lake Eyre, South Australia, and which he presented to the British 

 Museum (Geol. Dept., L. 9682), where it was determined years ago 

 by Mr. Etheridge, jun., as Moore's Cytherea clarkei. That specimen, 

 however, is i-ather more compressed, but allowing for certain 



