LEPTOGRAPTUS. 117 



overlap increase distally, so that eventually the inclination amounts to 25°, and 



the thecae are in contact for two-thirds of their 



Pig. 71 6. — Lept'ogravtws latus, sp. nov. -, ,-, 1T ,-. £ ,-, . .-,,, 



length. Hence the reason tor the increase in width. 



"l^C-tJ'-^r"'!*"^^ " Contrary to what obtains in most Leptoqrapti, the 



thecae are more distant in the proximal region 



Distal thee* Enlargement of part of (t we lve in 10 mm.) and closer set nearer the distal 



PI. XV I, fitf. 5 a. v / 



ends of the stipes (fourteen in 10 mm.). The 

 apertures are concave and oblique, and are situated in deep excavations. 



Affinities. — L. latus is allied to L. grandis in general form and size, but differs in 

 the more rapid increase in width of the stipes and in having a greater number of 

 thecae in the same unit of length. 



The habit and the form of the thecae in this species points in the direction of the 

 Dieellograpti. and it may possibly be regarded as a transitional form between the 

 two genera Leptograptus and Dicellograptus. 



Horizon and Locality. — Upper Llandeilo (Rorrington Flags). 



8. Shropshire : Spy Burn. 



Associates. — L. latus is found not infrequently in the Nemagraptus [Cmnograptus) 

 beds of Spy Burn, associated with Nemag. (Coenog.) gracilis, and also occurs rarely 

 at the same locality in the Leptog. validus beds above. The best specimens known 

 to us are in the collection of H.M. Geological Survey. 



Leptograptus ascendens, sp. nov. Plate XVI, figs. 6 a, b. 



Stipes narrow, flexed, generally crossing each other once in a length of 2 cm., 



widening gradually from origin to a width of rather less than 1 mm. Sicula 



long, narrow, with conspicuous apertural spine. Thecae narrow, ten to nine 



in 10 mm., inclined at 10°, about six times as long as wide, and free two 



thirds to one half their length. Apertural margins straight or slightly 



concave, occupying about one third the width of the stipe ; those of the two 



earliest thecae furnished with short spinous processes. 



The stipes diverge from a conspicuous sicula at an angle of about 270°, but 



generally show at once graceful convex curvature, and bend towards each other 



till they cross at a point about 1 cm. vertically above the sicula ; the stipe also is 



twisted on its own axis, so that the thecae continue to lie on the outside of the 



curve. 



The sicula measures about 1"2 mm. in length, exclusive of its apertural spine, 

 which is clearly defined; the spinous processes on th. I 1 and tli. I 2 are also of the 

 nature of apertural spines, but none of the later developed thecae have any 

 ornamentation of this nature. 



The thecae are well seen ; they widen slightly in the direction of their apertures, 



