Paheontology of the Older Tertiary of Victoria. 227 



Myoghama trapezia, sj). nov. 

 (Plate XII., figs. 8, 9.) 

 Shell trapezoidal elongate, moderately thick. Left valve free 

 and very slightly convex, convexity more niarked in the 

 neighbourhood of the umbo, umbo sharply pointed and incurved 

 immediately over the well marked triangular cartilage pit, 

 anterior margin straight, dorsal margin straight, making an 

 angle of 110° with the anterior margin and truncated at an 

 angle of 125° posteriorly, anterior and posterior margins slightly 

 rounded to join the convex ventral maigin. C)rnamented with 

 concentric ridges or corrugations separated by somewhat broader 

 shallow interspaces, a few faint radial wrinkles on the posterior 

 slope. Ptiglit valve convex, frequently only partially attached 

 by a limited portion of the dorsal surface, umbo free and 

 oi'namented with regular narrow concentric ridges, the concentric 

 corrugations of the unattached ventral poi'tion of this A'alve 

 generally not so well detined as those of the left valve, faintly 

 radially wrinkled anteriorly and posteriorly. 



Dijnensio?is. — Average right and left valves antero-posterior 

 diameter, 26 mm.; umbo-ventral diametei', 18 mm.; largest 

 example antero-posterior diameter, 29 mm. ; unib(j-\ eutral 

 diameter, 22 mm. 



Locality. — Eocene blue clays of Curlewis, Bellarine Peninsula. 

 — Six examples. Eocene, lower beds at Muddy Creek, near 

 Hamilton. — One example 



Observations. — It is only recently that any fossil s^^ecies of this 

 genus have been recorded from the Victorian Tertiaries. Professor 

 Tate, in a paper* on " Unrecorded Genera of the Older Tertiary 

 Fauna of Australia," describes and figures two new species under 

 this genus, M. plana from the Miocene of the Gippsland Lakes, 

 and Af. rugafa from the Eocene of Spring Creek, and of the 

 Gellibrand Kiver. The new species hei'ein described is closest 

 related to M. flana, Tate, but difters fi-om it most noticeably in 

 outline, and in the more regular and well-developed concentric 

 ridges, and in the absence of any umbonal radial corrugations. 

 The new species appears to be commonly only partially attached 

 by a limited portion of the dorsal region of the right valve to 



* Proc. P>OT. Soc. N.S.W., 1893. 



