486 MISS Gr. L. ELLES ON THE GKAPTOLITE [Aug. 1 898. 



There are twenty-four thecae in the space of an inch (nine to ten 

 in 10 mm.) ; they are free for one-third to half their length, and 

 make with the general direction of the stipe an angle of 30° to 40*^. 

 The apertures are straight and nearly perpendicular, being inclined 

 at an angle of 95° to 100°. 



The total length of primary and secondary stipes before dicho- 

 tomous division is about -^^ i^^^ (^'^ nim.). This measurement 

 represents the length of the so-called ' funicle ' of earlier authors, a 

 term, which as Holm has shown, is no longer applicable to the 

 graptolites. It is evidently celluliferous in some specimens, and 

 therefore, no doubt, in all. 



Whether the length of these branches of the 1st order is the 

 same on either side of the sicula I am not able to say with certainty ; 

 there is an appearance of symmetry in some aspects of the rhabdo- 

 soma, but this may be deceptive. It is unfortunate that, in almost 

 every case, this part of the rhabdosoma is preserved so that the 

 apertures of the cells are embedded in the rock, and only the dorsal 

 walls of the stipes are turned towards the observer. 



Occurrence. — This species is found in the Middle Skiddaw 

 Slates in the following associations : — 



(1) On a slab from Barf with Didymograptus Nicholsoni^ Lapw. 



(2) On a slab from Outerside with Cryptograptus Hopkinsoni, 



Nich. 



(3) On a slab from Bassenthwaite Common with Didymo- 



graptus gihberulus, Nich. 



(4) With Tetragraptus crucifer (Hall). 



Localities. — Barf; Outerside; Bassenthwaite Common ; Skid- 

 daw ; Randal Crag, Skiddaw ; Carlside Edge, Skiddaw : Aiken Gill 

 (Scawgill) ; Scale Hill, Crummock; north-east of Grrisedale Pike. 



(c) Teteageapttjs Headi (Hall). (Fig. 11, p. 487.) 



1858. Graptolithus Seadi, Hall, Geol. Surv. Canada Rep. 1857, p. 127. 

 1865. GraptolWnis Seadi, HaE, 'Grapt. of the Quebec Group,' Geol. Surv. 

 Canada, dec. 2, p. 94 & pi. vi, fig. 8. 



1868. Tetragrapsus Seadi, Nich. Quart. Journ. Geol. Soc. vol. xxiv, p. 131. 



I have not seen many specimens of Tetragraptus Headi from the 

 Skiddaw Slates ; three, or possibly four, which should be referred 

 to that species are in the Woodwardian Museum, but unfortunately 

 the stipes in all these are preserved with their dorsal side upper- 

 most, arid nothing is seen of the theea). The best specimen found 

 as yet is undoubtedly that in Mr. Postlethwaite's collection ; this 

 not only shows the disc well, but also one stipe is turned on its 

 side for part of its length and reveals the thecae. 



The general form of the species is similar to that of T. quadri- 

 hrnchiatus (Hall), but the dichotomoiis division of the primary stipes 

 seems to take place almost at once (in other words, the so-called 

 'funicle' is extremely short), and the stipes are wider than in that 

 species. The disc is quadrangular, nearly square, and with more or 

 less straight sides ; in the largest specimen examined it was fully 

 '^ inch (17 mm.) square, but often it is not completely preserved ; 

 it is always slightly extended along the stipes. In the specimen in 



