Dr. F. R. Coiuper Reed — The genus Homalonotus. 263 



the llecent seas of Brazil that the genus originated in Patagonia. 

 Since that date fossil representatives have been found in the West 

 Antarctic and in New Zealand, but in younger beds than the 

 Patagonian. Towards the end of the Miocene, then, the genus must 

 liave had a wide distribution in the Southern Ocean, which there is 

 considerable reason to believe was much warmer than at present. 

 Whether it attained this distribution by dispersion from Patagonia 

 or not is hardly a matter for profitable discussion at present, since 

 little or nothing is known of the Upper Cretaceous Brachiopods of 

 New Zealand and the Antarctic, 



s 



IV. — Notes on the genus ITomalonotus. 

 By F. R. COWPER Eeed, Sc.D., F.G.S. 



INCE Salter,^ in 1865, published his classification of the species 

 of the genus ITomalonotus, no detailed attempt has been made to 

 re-arrange the increased number of species now known into natural 

 groups. Salter was not convinced that his scheme was satisfactory, 

 and appears to liave regarded it as largely artificial, though con- 

 venient. The divisions instituted or recognized by him bore the 

 names Brongniartia, Salter, 1865 (^ivided into two sections); 

 IVimeriis, Green, 1832; Kceyiigia, Salter, 1865; Lipleura, Green, 

 1832 ; and Burmeisteria, Salter, 1865. 



Koch & Kayser,'^ in 1883, after describing the Lower Devonian 

 species of the genus from the lihenish area and other regions, 

 criticized Salter's system. The separation of Homalonotus and 

 IVimerus was not considered sound, but Bipleiira was acknowledged 

 to mark a distinct group. The Lower Devonian species were 

 grouped into two divisions, the first one containing two sub- 

 divisions, Homalonotus (which was regarded as equivalent to 

 Burmeisteria) and Triinerus; the second division was formed by 

 Dipleura. Primary importance was attached to the position of the 

 point of section of the lateral margin or genal angle by tlie facial 

 sutures, aiul secondary importance to the degree of furrowing of 

 the pygidium. In the first division the facial sutures cut tlie 

 margin in front of the genal angle, the thoracic axis is broader 

 than the pleural lobes, the pygidium is parabolic with a blunt or 

 pointed extremity, and has its axis and pleural lobes deeply 

 furrowed. The presence or absence of spines distinguished the two 

 subdivisions of this group. In the second division the facial sutures 

 cut the middle of the genal angles, the pleural lobes are as wide as 

 the axis, and the pygidium is bluntly rounded and either smooth 

 or only weakly furrowed. 



Bigot, Mn 1888, recognized three sections of the genus, for which 

 he employed Salter's group-names Brongniartia, Homalonotus sens, 

 str. {= Kxnigia), and Trimerus, but he revived Corda's name 



' Salter, Mon. Brit. Trilob., 1865, pp. 104, 105. 



2 Koch & Kayser, Abh. geol. specialk. Preuss., Bd. iv. Heft ii, 

 pp. 73-157, 1883. 



^ Bigot, Bull. Soc. Geol. France, ser. Ill, vol. xvi, pp. 419-35, 1888. 



