31 
Genus — T'ISSILUNULA/ gen. nov. 
Gen. Char. — Shell large, ovately-riiomhoidal, equivalve, inequilateral, 
moderately tumid, test thick. Umhones prominent, prosogyrate, inhent at 
their apices. Anterior ends compressed and produced. Lunule widely 
excavated, shallow. Articulus much thickened, a projecting hlunt cardinal 
tootli in the right valve slightly posterior to the umho, with a deep socket 
on either side, and an oblique posterior cardinal tooth ; two hlunt cardinal 
teeth in the left valve fitting into the sockets of the right valve, a deep socket 
between for the reception of the suhcentral cardinal of the right valve, and 
an oblique posterior cardinal socket ; lateral teeth unknown. Ligament 
amphidetic, parivincular, of two parts, one portion occupying the ligamental 
grove, the other part occupying a specially modified area beneath the umhones. 
Adductor scars well marked, particularly the posterior ; pedal scars feeble, 
pallia! lines well marked wdth the feeblest of sinuses and no pallia! tongues.- 
Sculpture concentric. 
Ohs. — I have ventured to propose this new genus for a shell that has 
always been a stumbling block to others as well as to myself. The history of 
the type species is as follows : — In 1870 the late Mr. Charles Moore, of Bath 
(Engl.), described some much mutilated bivalves from the Alaranoa lliver 
and AVollumhilla, in Queensland, and Gregory Creek, north of Lake Torrens, 
in South Australia, the largest of wdiich measured “ 6^ inches in breadth by 
4^ inches in depth to this he gave the name of Cytherea ClarkeV- Two 
years after Air. E. Etheridge described imperfect internal casts of a bivalv^e 
from the Upper Cretaceous beds of Alaryborough, Queensland, as Cyprina 
expansa^ collected by the late Air. Eichard Daintree. The figured specimen 
was somewhat smaller than those described by Air. Aloore. In my 
“Catalogue”^ I retained these under the names given by their respective 
authors, as I had not, at the date of publication of my work, seen examples 
of either. 
No further information seems to have appeared until 1889, when the late 
Prof. Ealph Tate, in his list of the Cretaceous fossils of the Lake Eyre Basin, 
united Cytherea Clarkei, Aloore, and Cyprina expanse, Etheridge, in one, 
adopting the former name. During several years anterior to the appearance 
' Fissum, a split or cleft, and lunula, a little moon (lunule). 
* Quart. Journ. Geol. Soc., 1870, XX\'I, p. 2.7((. 
> Ibid, 187-2, XXVIII, p. 338. 
‘ A Catalogue of Australian Fossils, &c., 1878, p. 108. 
