484 MISS G. L. ELLES ON THE 6EAPT0LTTE [Aug. 1 898, 



In the normal type with eight stipes of the 3rd order, there are 

 four short stipes of the 2nd order, and two short stipes of the Ist 

 order ; both stipes of the 1st order, and all four of the 2nd order, 

 undergo dichotomous division. 



In the septad type (seven stipes) one of the stipes of the 2nd 

 order fails to divide dichotomously, and persists as a single stipe : 

 the other three stipes of the 2nd order dividing as in the normal 

 type. 



In the hexad type (six stipes), two of the stipes of the 2nd order 

 show no dichotomous division, and in the pentad type (live stipes) 

 only one stipe out of the four divides dichotomously. Obviously 

 a further reduction gives rise to a form resembling a Tetragraptus 

 of the quadrihrachiatus-tyi^e. On this point more will be said 

 later. 



The stipes of the 1st order are about -^ inch (1-05 mm.) in 

 length, those of the 2nd order about -J-g- inch (1'58 mm.), while those 

 of the 3rd order are often very long, some attaining a length of 

 from 5 to 6 inches (12* 6 to 15 cm.) ; others, younger perhaps, 

 barely exceed an inch (25*39 mm.) in length. The stipes are slender 

 at their origin, but widen out to a maximum of ^ inch (3*17 mm.) 

 in the larger forms ; naturally the smaller ones are not so wide as 

 this. 



The thecae on the stipes of the 3rd order, which are the only ones 

 clearly seen, number between twenty and twenty-four to the inch 

 (eight to nine in ] mm.) ; they are 4 times as long as wide, and 

 are inclined at an angle of about 20° at their bases, curving so that 

 near the aperture the cell makes an angle of 50*^ to 55° with the 

 axis of the stipe. The thecae are in contact for two-thirds of their 

 length, and their apertures make an angle of 105° to 110° with the 

 general direction of the stipe. 



A disc may or may not be present, and when present varies 

 greatly in size in different individuals. 



Occurrence. — The species occurs in the Middle Skiddaw Slates, 

 on slabs associated with Didymograptus nitidifs, D. patulits, D. gih- 

 bgrulus, D. V-fr actus, Tetragraptus sp. ?, and Loganograptus (nonad 

 type). 



Localities. — Eandal Crag, Skiddaw; Mire House, Skiddaw; 

 Carlside Edge ; Slape Crags, above Hope Gill, Brackenthvvaite ; 

 Outerside ; Braithwaite ; Grisedale Pike. 



DlCHOGEAPTirS SEPARATUS, Sp. UOV. (Fig. 10, p. 485.) 



There are two slabs of this species in the Woodwardian Museum. 

 It is a somewhat rigid and very slender form, and is characterized 

 by the unusual length of the stipes of the 1st order, which are 

 much longer than in any form of Dichograptus hitherto described. 

 Each stipe must be fully J inch (3*17 mm.) long, and thus what older 

 authors would have regarded as the ' funicle ' is | inch (6.35 mm.) 

 in length. The two stipes of the 2nd order make with each 

 other an angle of 105° ; these are rather less than ^ inch in length ; 



