20 Mr. R. Etlieridge on a Species o/" Terebratella. 



valves unequally convex. Ventral valve longitudinally and 

 obtusely carinate, convex, and tapering towards the beak, 

 which is a little incurved, truncated by a slightly oblique cii-- 

 cular foramen ,• beak-ridges sharply defined, enclosing between 

 them and the hinge-margin a Avide triangular area, flat or 

 a little concave. Dorsal valve depressed, with a gentle curve 

 from the umbo to the front ; but in some specimens a slight 

 longitudinal depression or sulcus exists towards the centre of 

 the valve, extending to the front ; hinge-line in some indi- 

 viduals a little curved, in others almost straight, giving to the 

 valve a somewhat triangular form. Surface with a few con- 

 centric lines of growth. Shell-substance thin, punctate. 

 Length 8 lines, width Q\ lines, depth 4 lines. 



Ohs. Fig 5, c?, representing the interior of the dorsal valve, 

 exhibits some of the characters on which the reference of 

 this species to the genus Terehratella is based. At the end of 

 the median septum may be seen the broken horizontal process 

 to which the loop would be attached in the perfect specimen. 

 The oral processes, instead of being directed inwards towards 

 the septum, are pointing forwards directly parallel to it. The 

 above are the measurements of the largest specimen I have 

 seen. 



Loc. and Horizon. Coralline Limestone of Mount Gambler, 

 S. A. Coll. Geol. Soc. London. 



T. compta was originally figured by Capt. Sturt from a 

 specimen obtained from the Coralline Limestone of the Murray- 

 River Cliffs, near the Great Bend, S. A. Count Strzelecki's 

 example, upon which Mr. G. B. Sowerby'-s description is 

 founded, was obtained from a raised beach at Port Fairy. 

 The Rev. Mr, Woods has recorded it from Mount Gambler *, 

 S. A. ; whilst Mr. C, S. Wilkinson has obtained it in consider- 

 able numbers from the Spring-Creek f section near Geelong, 

 Victoria. 



The following brief description of the appearance and extent 

 of the Mount-Gambier Coralline Limestone is abstracted from 

 the Rev. J. E. Woods's excellent work, ' Geological Obser- 

 vations in South Australia' % : — 



Immediately under the surface of the country in the Mount- 

 Garabier district is usually found a brittle white limestone, 

 much decomposed and without fossils, which gradually passes 

 downwards into a hard and close perfectly white rock, 

 horizontal, and distinctly stratified in layers or beds about 



* Quart. .Journ. Geol. Soc. 1860, xvi. p. 255 &c. 

 t Cape-Otwav Report, 18G5, p. 28. 

 X Pp. 58-125. 



