Vol. 54.] FATJNA OF THE SKIDD AW SLATES. 493 



Localities. — All the specimens known to me come from 

 Carlside Edge or Barf, and all except one are in Mr. Postlethwaite's 

 collection, the one other specimen belonging to Prof. Nicholson. 



I name this species after my friend Mr. Postlethwaite, who first 

 pointed the form out to me, and to whom all geologists owe a debt 

 of gratitude for his arduous labours among the Skiddaw Slates. 



Genus Phyllograptus, Hall. 



(c) Phyllograpttjs ilicifolius, HaU, 



I860. Fhyllograptus ilicifolius. Hall, 'Grapt. of the Quebec Group,' Geol. Surv. 

 Canada, dec. 2, p. 121 & pi. xvi, tigs. 1-10. 



The rhabdosoma consists of four stipes, united so as to form two 

 broad intersecting ovals, each of which is widest at its upper end. 

 The rhabdosoma is about J inch (12-7 mm.) long, and has a 

 maximum width of | to ^ inch (6*4 to 7*5 mm.). The curvature of 

 the thecse in different parts of the rhabdosoma is very characteristic : 

 near the proximal end they first ascend, and then curve out and 

 down ; in the centre of the rhabdosoma they are so little curved 

 that they appear almost horizontal ; while at the distal extremity 

 they are directed outwards and upwards, and ultimately almost 

 straight upwards. The thecse number thirty-two to the inch 

 (thirteen in 10 mm.) ; they are in contact throughout their length ; 

 their apertures are concave, oblique, and distinctly mucronate. 



Occurrenc e. — With Phyllograptus typus in the Middle Skiddaw 

 Slates (upper part). 



Locality. — Eandal Crag. 



{d) Phyllogeaptus ilicifolius, Hall, var. geandis nov. 



The general form of the rhabdosoma is the same as in the foregoing, 

 and consists of four stipes united so as to form two broad inter- 

 secting ovals. The rhabdosoma is fully 1 inch (25*4 mm.) long, 

 and has a maximum width of -^-^ inch 



(14*7 mm.). The curvature of the thecse Pig. 15. — Phyllograp- 

 and the number to the inch agree with tus ilicifolius, var. 

 P. ilicifolius. Growth-lines parallel to the grandis nov. {coll. 

 thecal aperture are seen on several of the Woodivardian Mus.). 

 thecae. 



The specimen upon which the above 

 description is based is in the Woodwardian 

 Museum ; it is very much larger than any 

 specimen figured by Hall as belonging to 

 the species ilicifolius ; in fact, it resembles 

 most closely those figures which are en- 

 larged 3 diameters. I have therefore 

 designated it as a variety of Hall's species, 

 and given it the name grandis to denote [Nat. size.] 



its unusual size. 



Locality. — North-east of Sleet How, Keswick. 



