546 NEW BKACHIOPODS FROM THE MIDDLE PALAEOZOIC ROCKS, S.S.W., 



of the shell; area short, narrow, and usually contracted by pressure; cardinal 

 angles mildly rounded. Front margin strongly sinuate. 



Dimensions. — Length 18 mm., width 29.7 mm., depth 12.5 mm. 

 Length 21.9 mm., width 32.8 mm., depth 15.6 mm. 



The first of these measurements is of a very perfect specimen three-fourths 

 grown. The other is of an adult specimen. The different dimensions do not 

 seem to bear proportional relations in either case. 



Obs. — This Spirifer belongs to Hall and Clarke's group I. Radiati, and sec- 

 tion 1, Pauciplicata of that group, approaching closely to ,S. radiatus and S. 

 plicatellus Sowerby externally; but more to the latter than the former, more espe- 

 cially to the Swedish representatives of the species. In a less degree it resembles 

 5. eudora Hall, from the Niagara formations; but dimensionally is very different. 

 Both S. radiatus and N. plicatella differ from the local species in the absence of a 

 medial sinus on the fold of the brachial valve. The radial ribs of the former 

 are not prominent, and diminish in this respect as they approach the umbo in 

 the latter; they are very prominent throughout their length, except, in the case 

 of the outer rib or two on each valve. The hinge lines and areas of 

 the two species are much alike. In adult specimens of the Bowning 

 one there are constantly six ribs on each side of the sulcus on the pedicle valve; 

 and on each side of the medial fold of the brachial valve, the ribs are five. In 

 the case of S. plicatella Sow. the ribs on the similar parts seem to be more variable 

 in number and in prominence. The two are easily separable from each other. 

 and the same may be said of S. radiattis and the local one. 



This Spirifer is very characteristic of the Lower Trilobite Beds of the Bown- 

 ing Series, where it is common and has very few other Spirifers for associates, 

 but instead, numerous trilobites, among which are Od-ontopleura bowningensis E. 

 and M., O. parinssirrm E. and M., Ceratocephala rngdesi E. and M., Sphaer- 

 exochus mirus Beyrich, Stauroceplinlus murchisoni Barr.. etc. 



It is one of the few representative members of the fauna of the Lower Trilo- 

 bite Beds that pass upward into the Middle Trilobite Bods; and probably sur- 

 vives to the lower Devonian period, for some fragments of a Spirifer near to. if 

 not identical with it, have been collected from the limestones near the junction of 

 the Goodradigbee and Murrumbidgee Rivers. 



Loc. and horizon. — Lower and Middle Trilobite Beds, Bowning, Parish of 

 Bowning, Countv Harden, N.S.W. Upper Silurian — Wenlock or Barrande's etage 

 E. 



M o LO X r, I A, n.gen. 



The Bowning and Molong districts of New South "Wales yield a Spiriferoid 

 Brachiopod which T have been unable to place in any of the genera of this large 

 group. It possesses a well-defined smooth sulcus in the pedicle valve and an 

 eciually distinct median fold in the brachial valve: the spiralia too are very like 

 those of true Spirifers. But they have no cardinal area, neither is an open 

 delthyrium present; but, instead, there is a foramen truncating the apex of the 

 ])edicle beak. It seems not distantly related to Hall's genus Trematospira, but 

 it lacks some of the essential features of that genus, for instance, its shell is 

 imperforate and within the sulcus of the pedicle valve there are no folds. Failing 

 to be satisfied that it can be i)laced in any existing genus, a new genus is proposed 

 for its reception . 



