Vol. 54.] 



PATINA OF THE SKIDD AW SLATES. 



521 



The species is characterized by the spinous processes at its 

 proximal end, which are very similar to those in Cryptograptus 

 antennarius (Hall), but are more curved and less rigid than in that 

 species. 



The thecae, with their slightly reflexed denticles, are also peculiar ; 

 they number twenty-four to the inch (nine to ten in 10 mm.). 



Occurrence. — With Tetragraptus quadrihrachiatus (Hall) and 

 Didymograptus indentus (Hall) in Middle and Upper Skiddaw Slates. 



Localities. — Outerside; EannerdaleFell; GlenderamakinYalley. 



Fig. 82. — Glossograptus fim- 

 briatus, /rom Ellergill; coll. 

 J. E. Marr. 



Genus Glossograptus , Emm. 



(c) Glossogeapttjs riMBKiATTJs (Hopk.). 



1872. Diplogra'ptus Jtmhriatus, Hopk. Geol. Mag. vol. ix, p. 506 & pi. xii, fig. 8. 



There are at least three specimens of this species in the Wood- 

 wardian Museum, and one from Ellergill is extremely well preserved. 

 The specimens have a length of | inch (12'7 mm.), exclusive of the 

 distal prolongation of the virgula, which is seen in one specimen 

 for -^ inch (4*2 mm.) beyond the distal extremity of the rhabdosoma. 

 The sides are parallel, and the vddth about y^^ inch (1*58 mm.), 

 exclusive of the spines. This width 

 is maintained throughout the length 

 of the rhabdosoma. 



The thecse number forty to the inch 

 (sixteen in 10 mm.) in the proximal 

 part of the rhabdosoma, but about 

 thirty-six (fourteen in 10 mm.) 

 nearer the distal end. They are 

 narrow tubes, expanding in the 

 direction of the aperture, and their 

 length is about 3 times as great as 

 their width. They are in contact 

 for about half their length, and are 

 inclined at a low angle of about 20°. 

 oblique. 



The spines are thick, especially at their bases ; they are about 

 ^0- inch (1*26 mm.) long, those near the proximal end are directed 

 outwards and downwards, tliose in the centre of the rhabdosoma 

 are horizontal, while those near the distal end are directed outwards 

 and upwards. The actual base of the specimens is not very clear, 

 but the spines there seem to be directed vertically downwards. The 

 course of the virgula is clearly indicated. 



This species differs from Gl. armatus — (1) in general form ; (2) in 

 the possession of more numerous thecse in a given unit of length ; 

 and from Gl. Hincksii (1) in shorter spines ; (2) in the possession of 

 more numerous thecae in a given unit of length ; (3) in the greater 

 width attained by the rhabdosoma. 



Occurrence. — Ellergill Beds = Upper Skiddaw Slates. 



Localities. — Ellergill; Mosedale Beck, near Troutbeck ; Barf. 



[Nat. size.] [x5.] 

 The apertures are slightly 



