74 Proceedings of the Royal Society of Victoria. 



Observations. — This species resembles in its superficial ornament 

 both Plectambonites corrugata, Poi'tlock sp./ and P. interstrialis, 

 Phillips sp." Our specimen is more globose in the ventral valve 

 than either of the species just mentioned. As regards the orna- 

 ment P. corrugata has both primary and secondary radii, and 

 from four to seven intercostal striae, whilst the Gippsland 

 species has the costae running the entire length of the valve 

 and the intercostal striae are nearly twice as many. It 

 differs from P. interstrialis in much the same details, and also 

 in having a proportionately longer shell. It is noteworthy that 

 P. corrugata is found in the Llandeilo and Bala series (Ordovic- 

 ian) in the British Islands, and also in Bohemia, whilst P. inter- 

 strialis comes from the middle Devonian of Devonshire and the 

 Eifel. 



Occurrence. — In a dark blue limestone, having a semi-crystalline 

 appearance due to numerous cleavage surfaces of crinoidal joints 

 and ossicles. Deep Creek, seven miles S.W. of Walhalla, 

 Gippsland. Collected ^nd presented to the National Museum, 

 together with other specimens of much interest from the same 

 locality, by the Rev. A. W. Cresswell, M.A., in whose honour 

 the species is named [669-70]. 



Horizon. — Silurian (Yeringian). 



Genus Chonetes, Fischer. 



Chonetes melbournensis, sp. nov. (Plate XI., Figs. 2-4). 



Specific characters. — Shell transversely elongate, semi-circular in 

 outline ; sub-plano-convex. Brachial valve approximately flat or 

 only slightly concave ; surface with numerous tine threadlike 

 and radial striae ; cardinal process prominent. Pedicle valve 

 with surface traversed by 7 or 8 threadlike radii and numerous 

 finer striations in the interspaces. Sometimes the radii are 

 obsolete, the tine striae alone prevailing. Posterior margin of the 

 pedicle valve bearing about 10 slender spines, often having a 



1 Ortkis comugata, Portlock, 1843, Rep. Geol. Londonderry, etc., p. 450, pi. xxxii., figs. 

 17, 18. Strnphomena corrwjateUa, Davidson, 1871, Brit. Sil. Brach., No. iv. (Pal. Soe. 

 Mon.), p. 301, pi. xli., figs. 8-14. 



2 Orthin interstrialis, Phillips, 1841, Palaeozoic, Foss. of Cornwall, Devon, and West 

 Somerset, p. 61, v>l. xxv., fig. 103. Leptaena interstrialis, Phil, sp., Davidson, 1865, Brit. 

 Dev. Brach. (Pal. Soc. Mon.), p. 85, pi. xviii., figs. 15-18. 



