Br. F. R. Coiuper Reed — The genus Homalonotus. 267 



glabella, such as Salter' specially noticed in the South African species 

 jff. fferscheli, are also present in H. delphinocephalus ; these areas may 

 be marked off by a faint curved furrow or have a slight independent 

 convexity, but are also distinguished from the rest of the cheeks by 

 their smoothness and absence of pitting. They may be termed the 

 paraglabellar areas (for further remarks see Jioetu'ffia and Btirmeisteria). 

 The epistomal sutures are very short on the upper surface of the 

 head-shield and usually difficult to distinguish, but they are at right 

 angles to the conjoint facial sutures and arise in front at a distance 

 apart rather less than the anterior width of the glabella. 



The course of the facial sutures themselves on the head-shield is 

 usually well seen ; Hall (op. cit.) describes them as " parallel and 

 coincident with or slightly Avithin the flexure of the margin, passing 

 then obliquely through the eyes and turning [to] come to the margin 

 a little above the posterior angle of the head-shield ". They meet in 

 front on the upper surface at an angle forming a more or less pointed 

 Gothic arch close to the anterior margin and leaving a wide area 

 before the glabella. 



In one specimen in the Sedgwick Museum (Tablet Ko. 114) from 

 the Wenlock Shale of Dudley, the inferior surface of the front part of 

 the head-shield is shown ; the doublure, which is broad, flattened 

 and subcrescentic in shape with the posterior margin forming a 

 double sigmoidal curve, reaches back to the front end of the glabella ; 

 the epistomal sutures are straight and converge posteriorly, thus 

 defining a flat elongated triangular epistome which does not appear 

 to have been described or figured in the case of British examples of 

 the species. 



In the case of the thorax of the type-species it should be mentioned 

 that each segment of the axis has an anterior articulating baiid 

 which is separated off by a furrow which bends back gradually before 

 reaching the axial furrows and crosses the pleura obliquely. The 

 axial furrows of the thorax are not in the same longitudinal line as 

 those defining the glabella, for the axial furrows of the head-shield 

 on crossing the occipital ring diverge obliquely outwards. There 

 are, however, no well-defined axial furrows at all on the thorax, 

 faint longitudinal depressions only being present in conjunction with 

 a slight constriction of the pleura. At this point also, on each 

 segment, there is situated the inner angle of the large triangular 

 articulating facet extending to the end of the pleura and forming 

 a bevelled flattened surface with a sharp, angulated posterior edge 

 which crosses the pleural furrow obliquely without diverting its 

 course. Barrande's^ figure of a body-ring of H. delphmocephalus 

 gives an erroneous idea of its characters, for it fails to show that the 

 furrow which marks off the articulating band on the anterior of the 

 axial ring, is continued across the pleura and articulating facet as 

 the pleural furrow. Hall (op. cit.) describes it more clearly than 

 Salter, who does not make it plain that this furrow is continuous. 



Of other species referable to this section Salter mentions two, 

 S. Johamiis, Salt., and S. ci/lindricus, Salt., both from the Silurian. 



^ Salter, Trans. Geol. Soc, ser. II, vol. vii, p. 216, pi. xxiv, fig. Ic, 1856. 

 ^ Barrande, Syst. Silur. Boheme, vol. i, pi. v, fig. 10. 



