544 NEW BRAt'HIOFOUS FROM THK MIDDI.K PALAEOZOIC ROC'KS, N.S.W., 



occurs with these same Atrypids at Hatton's Corner in the Bi)unyonj^ian Beds 

 but the Hatton's Corner species has not yet been obtained from the Moloner Beds. 



Spirifer houningensis is very characteristic of the Lower Trih)bite Beds of 

 the Bounyongian Series, and is also one of the few individuals of the fauna of these 

 lower beds which survive to app.?ar in the Middle Trilobite Beds. 



If the suspected occurrence of the genus Seminula should be i)roved an ac- 

 tuality in this Gunneubene limestone patch, an uiiusiuU cDinininirlinsj of Devonian 

 and Carboniferous genera would be the result . 



It may not be out of place here to remark how vi'ry iMi])nrtaiit a help it 

 would be towards the completion of a satisfactory geological survey of the State, 

 if full and systematic palaeontographies were made of the stratified rocks of 

 Moloug, Wellington, and Orange in conjunction with tliose of the Bounyongian 

 Beds. Besides, a work of this kind would without doubt result in many valuable 

 palaeontological discoveries being made; for the .stratified rocks of these localities 

 are not to be suri)assed for fossiliferous wealth. 



Family MERISTELLIDAE Waagen. 



Merista plebeia Sowerby. (Plate xxxi., tigs. 13.) 



Spec. Char. — Shell biconvex, subtriangular, valves about equally convex, 

 smooth. Pedicle valve a good deal deeper than the brachial one, strongly convex 

 especially in front of the umbo; anteriorly depressed umlione pi'ominent, incurved 

 apically, truncated by a circular foramen. Brachial valve slightly more convex 

 than the pedicle valve; in some specimens a very inconspicuous fold is present; 

 umbo modeiately prominent, strongly incurved, and overhung by that of the 

 pedicle valve; a well developed septum present. Hinge line mildly arcuate. 

 Cardinal angles l)luiit. Lateral and front margins very mildly sinuate. Only 

 a small portion of the brachidium has been observed in one specimen. 



Diuieiisiotis. — Four individuals gave tlic following measurements: — 

 Length 18.7 mm. Width 18.7 mm. Depth 11.7 mm. 



17.3 .. 17.3 „ 10.2 



,, 15.fi „ 15.2 „ n.4 



„ 15.6 „ 15.2 „ 0.4 



But while these four specimens yielded fairly constant piniiortions for tlie 

 three dimensions tlie following did not: — 



Length LM.lt mm. Width 17.2 mm. Deptli 12. .5 mm. 



20.85 „ 18.23 ,. 12.5 



21.9 „ 21. n „ 



These variable dimensions do not afford int'onnaticn of much value in de- 

 termining' its specific position. 



f)I>s. — The form now dealt witli licars close rdationsliip exteinally to ."If 

 vleheia Sow. sp. and to If. lenncfseeimis Hall and Clarke, yet diffeis in some 

 respects from both. 



Dimensionally, the adult specimens of .1/. plebeia and the local form closely 

 agree in size as is sluiwn by a comiiarison of the measurements of the two forms. 

 The dimensions of .1/. plebeia given by Davidson for two specimens arc (Brit. 

 Fos.s. Brach.. iii. 1804-71. PI. iii.. figs. 2-10)- 



Length 18.75 mm. Widtli 20.8 mm. Dci.th 10.4 ,„;n. 



20.8 ,. 10.5 ., 12.5 



