PLATE XXVIII. 



Sub-genus Orthograptus. 

 Figs. 



1 a — <1. — Orthograptus quadrimucronatus (Hall). (Page 223.) 



1 a. Typical specimen, characteristic sub-scalariform view. Mt. 



Benger Burn, S. Scotland. Hartfell Shales. Lapworth's 



Collection. 

 1 1>. Specimen showing distal prolongation of virgula, dominant bi- 



profile view. Hartfell Spa. Hartfell Shales. Wood's Collection. 

 1 c. Bi-profile view, spines fore-shortened. Mt. Benger Burn. Hartfell 



Shales. Lapworth's Collection. 



1 d. Large specimen, dominant bi-profile view. Hartfell Spa. Hartfell 



Shales. Lapworth's Collection. 



2 a — (/. — Orthograptus quadrimucronatus, var. spinigerus, Lapworth. (Page 225.) 



2 a. Long typical specimen. Hartfell Spa. Hartfell Shales. Lap- 



worth's Collection. 

 2 b. Smaller specimen, showing six large spines. Ibid. 

 2 c. Typical specimen, bi-profile view. Ibid. 



2 d. Small specimen, characteristic sub-scalariform view. Mt. Benger 



Burn. Hartfell Shales. Lapworth's Collection. 



3 a — c. — Orthograptus Pageanus, Lapworth. (Page 225.) 



3 a. Complete and typical specimen. Hartfell Spa. Hartfell Shales. 



Lapworth's Collection. 

 3 b. Smaller specimen. Ibid. 



3 c. Ditto. On same slab as fig. 3 b. 



4 a — c. — Orthograptus Pageanus, var. micracanthus, Elles and Wood, nov. (Page 



226.) 



4 a. Typical specimen with virgular tube split. Hartfell Spa. Hartfell 



Shales (zone of Dicranog. Glingani). Lapworth's Collection. 

 4 b. Specimen slightly narrowed by compression. Ibid. 



4 c. Two specimens in natural position on rock. Ibid. 



5 a. — Orthograptus Pageanus, var. abnormdspinosus, Elles and Wood, nov. (Page 



226.) 



5 a. Group of specimens in natural position showing typical form. 



Hartfell Spa. Hartfell Shales. Lapworth's Collection. 



