NEWTON : OPAUZED SHELLS OF NEW SOUTH WALES. 225 



variations whicli exist in the species, it would appear reasonable to 

 regard the example from White Cliffs as belonging to the same form. 



Locality. — White Cliffs, New South Wales. 



Collection. — British Museum (Geol. Dept., L. 21274). 



Distribution. — Lower Cretaceous: New South Wales, Queensland, 

 and South Australia, "Upper Cretaceous: Queensland and South 

 Australia (Lake Eyre region). 



Fam. PTEEIID^ {- Aviculidse). 



Maccoyella baeklyi, Moore, sp. PI. VI, Fig. 19. 



Avicula harklyi, Moore, Quart. Journ. Geol. Soc., vol. xxvi, p. 245, 



pi. xi, tigs. 1, 2, 1870. 

 Avicula alata, Etheridge, Quart. Journ. Geol. Soc, vol. xxviii, p. 342, 



pi. XX, fig. 8, 1872. 

 Monotis bar/di/i, Tate, Trans. Roy. Soc. South Australia, vol. iii, 



p. 179, 1880. 

 Maccoyella barklyi, Etheridge, jun. : Jack & Etheridge, Geology 



and Palaeontology of Queensland, 1892, p. 455, pi. xxii, 



figs. 1-5 ; pi. xlii, figs. 4-6 ; pi. xxiii, figs. 1-2 ; Mem. Geol. Surv. 



N.S.W., Paleontology, 1902, No. xi, p. 17, pi. ii, figs. 3-5; 



pi. iii, figs. 4, 5 ; pi. iv, figs. 3, 4. 

 Description (^original). — Shell slightly inequilateral, orbicular, large 

 valve convex, small valve flattened, umbones pi'ominent ; auricles 

 rather small, nearly equal. The large valve slightly produced 

 posteriorly and ornamented with 24 radiating costae, which are more 

 raised and appear spinous on the posterior margin. The small valve 

 slightly convex with a very distinct oi'naraentation from the larger, 

 the costoe being much finer, and about 44 in number. The costae are 

 decussated by numerous regular concentric lines of growth, which, 

 when they meet, give them a nodulated aspect. The lines of growth 

 have been reflected or folded over the anterior auricle and side, which 

 gives the shell a very pecidiar appearance. The small valve possesses 

 a large and deep groove for the passage of a byssus. The punctate 

 structure of the Aviculidae may be clearly distinguished, by aid of the 

 lens, in this species. 



Remarks. — The specimen referred to this species exhibits an external 

 view of a left valve which is so attached to the matrix that all internal 

 characters are concealed. It is of medium size, slightly convex, with 

 au umbo well above the dorsal line ; the margins are fractured and 

 imperfect, especially posteriorly, while the ventral border is rounded. 

 Although much eroded the surface has still preserved some thirteen 

 equidistant, primary, radial costae, an obscure secondary rib dividing 

 equally the intercostal spaces being occasionally present, and seen only 

 in the later development of the shell, and whicli is not observable on 

 the umbonal region. Numerous close, concentric striatious form part 

 of the ornament of the valve, and where they cross the radial costae 

 minute nodulations are produced. 



Dimensions {approximate). — Length 40, height 38 mm. 

 We are indebted to Mr. Etheridge, jun., for our later knowledge of 

 this species, which he made the type of his genus Maccoyella (Jack 



