182 F. Chapman and Irene Crespin: 



Rhynchonella squamosa, Hutton, Denant and Kitson, 1903, 



p. 129. 

 Acanthothyris squamosa, Hutton sp. Chapman, 1914, p. 167,. 

 fig. 89F. 



Description. — In his paper on the Tertiary Deposits of Australia, 

 Tenison Woods gives a very brief description of the species which 

 McCoy indicates as the typical Victorian form. Tenison Woods' de- 

 scription is as follows: — " Rounded trigonal, with a strong mesial 

 fold, with many fine imbricated ribs." A note is added from McCoy 

 " from several Miocene beds in Victoria." 



Davidson remarks on the relationship of this to the recent form, 

 T. nigricans, from New Zealand. " Some examples in external shape 

 cannot be distinguished, but I have not observed on any recent 

 R. nigricans such prominent and strongly marked imbricated striae. 

 The fold and sinus seem more strongly marked on the fossil form. 

 The ribs also seem smaller and more delicate than on real nigricans."^^ 



Sj)ecific Characters. — Shell suborbicular, more or less transversely 

 elongated. Ventral valve depressed with a deep sinus. Dorsal valve 

 strongly convex, with a more or less flattened median fold. Umbo 

 rounded, not prominent. Pedicle area truncated. Foramen ovate, not 

 large. Deltidial plates triangular, with slightly vertical prolongation; 

 slightly discrete. The area of the valves near the lateral commissure 

 compressed. Average number of plicae on sinus, 8; on ventral, 36 to 40. 



Dimensions. — Specimen a. — Length, 14 mm.; width, 17 mm.; thick- 

 ness of valves, 9mm. Greatest width of delthyrium, 1.25. 



Specimen &. — Another specimen (figured), length, 16 mm.; width, 

 18 mm.; thickness of valves, 8.5 mm. 



Observations. — This Victorian rhynchonellid has long been held 

 to be identical with the New Zealand species which Hutton described 

 as R. squamosa. In various references made subsequently there have 

 been allusions to the several points of difference between the Vic- 

 torian and New Zealand specimens. From the very fine series placed 

 at our disposal by Mr. F. A. Cudmore, which he collected at Table 

 Cape, Tasmania, in addition to those which we have in the National 

 Museum collection, and others recently collected by us from the iron- 

 stone beds of Green Gully, Keilor, we are enabled with some degree 

 of certainty to refer the Victorian specimens of the type to the 

 original species of Tenison Woods. 



This species is found in the Tasmanian " Crassatellites bed " in 

 company with our new species, T. thomsoni, of which the description 

 follows immediately. In that description also will be found a synopsis 

 of the characteristic differences between these two forms. As we 

 have already shown, the shape and ornament, such as number of 

 costae, separate T. coelata from Hutton's species T. squamosa. 



Occurrence. — Oligocene. Muddy Creek, rare. Recorded by Tate. 



Miocene. — Tasmania. — Crassatellites bed, Table Cape. South Aus- 

 tralia. — Aldinga (Glauconitic Limestone) ; Muloowurtrie, near Ardros- 



13. See. Woods, J. E. T., 1878, p. 77. 



