226 BRITISH GRAPTOLTTES. 



The virgula is always very conspicuous, and is stiff and wire-like. 



All the thecae are provided with conspicuous spines, but those on the basal 

 thecae are specially long and may measure as much as 4 mm. The apertural 

 margins of the thecas are conspicuously lobate and approximate to those of 

 Orthog. calcaratus. 



Affinities. — 0. Pageanus is undoubtedly closely allied to 0. quadrimucronatus, 

 but differs from it in being shorter and broader, and having more closely set 

 theca), which are also somewhat different in form and ornament. 



Horizon and Localities. — Hartfell Shales (zone of Dicranog. Cling ani). 



S.Scotland: Hartfell; Auchenacat Burn. 



Collect ion. — Lapworth. 



Var. micracanthus, var. nov. Plate XXVIII, figs. 4 a — c. 



Associated with 0. Pageanus there occurs a shorter and narrower form which 

 is sufficiently distinct to rank as a variety. 



This form never exceeds 3 cm. in length. The 

 polypary widens rapidly from a broadly truncate 

 base, attaining its maximum breadth of 2*5 or 3 mm. 

 within 5 mm. of the proximal end, and this is main- 



Fio. 118. — Orthograptus Pageanus, var 

 micracanth us, nov. 



tained for the remainder of its length. 



Horizon and Localities. — Hartfell Shales (zone 

 of Dicranog . Clingani). 



S. Scotland : Hartfell; Dobb's Linn. 



Associates, etc. — Var. micracanthus is fairly 

 common in the zone of Dicranog. Clingani, where it 



Proximal end, showing origin of septal 



groove. Enlargement of part of occurs associated with Ortlioq. calcaratus and other 



PI. XXVIII, fig. 4 6. 



forms. 

 Collections. — Lapworth and the Authors. 



Var. abnormispinosus, var. nov. Plate XXVIII, fig. 5 a. 



A second variety, which may be appropriately named abnormispinosus, bears 

 precisely the same relationship to 0. Pageanus var. micracanthus that 0. quadri- 

 mucronatus var. spinigerus does to its typical species. It occurs in the zone of 

 Dicranog. Clingani. This variety never appears to exceed 2*5 cm. in length, 

 and has abnormally developed spines on the eighth or ninth thecal pair, or more 

 rarely on a few other thecal! also. It widens gradually throughout its length, 

 attaining its maximum breadth of 3 mm. close to the distal extremity. The theca? 

 are somewhat less closely set than in 0. Pageanus, being fourteen to ten in 10 mm. 



