LEPTOGRAPTFS. Ill 



outward at a wide angle of about 250°, and their slight curvature is variable in 

 direction and amount; they are characteristically narrow, but widen somewhat in a 



distal direction, having a width at their origin not 

 Fias. 65 a ^di^Leptog^tusfiaccidus, exceeding .3 mm ? and a maximum breadth near the 



J J distal end of "6 mm. 



The sicula is a long tapering cone about 2 mm. 

 in length, exclusive of the noma, which is occasion- 

 6 ally preserved; the origin of the stipes is basal, and 



a. ob/erse view. tne ^ rst thecse grow at once obliquely outward, 



b. Reverse view^Botti on same slab as gi vmg a c h arac teristic look to the proximal end; 



thecse l 1 and l 2 are furnished with a small spine. 

 The thecse are very long and narrow, and are more remote than in any other 

 species of Leptograptus. There are six in 10 mm. 



Fig. 65 c.-Leptograp^ flaccidus, var. ^^ ^ greater part of the ]en „ {h Q f the gtipeSj 



__ but eight in 10 mm. quite close to the sicula; they 



have an average length of 2- 5 mm., and their 

 Distal theea^ Element of P art of apertures occupy about one-half the width of the 



stipe. 



Affinities. — Var. macer perhaps resembles var. macilentus more closely than any 

 other variety of L. flaccidus. The resemblance lies in the length of the sicula and 

 the character of the proximal end ; it may, however, be readily distinguished from 

 that variety by the remoteness of its thecae and the greater tenuity of its stipes. 



Horizon and Localities.- — Lower Hartfell Shales (zone of Pleurog. linearis). 



S. Scotland : Hartfell Spa; Belcraig Burn. 



Associates, etc. — Var. macer occurs in some abundance in the upper zone of the 

 Lower Hartfell Shales, where it has been found in association with L. flaccidus, 

 L. capillaris, Diplog. truncatus, Biplog. foliaceus, var. vulgatus, and Climacog. 

 tubuliferus. 



Good specimens are in the collections of Lapworth and the Authors. 



Var. arcuatus var. nov. Plate XV, figs. 3 a — c. 



Another variety of L. flaccidus shows marked curvature of its stipes, and 

 generally approaches the sigmoid form characteristic of L. capillaris. The stipes 

 are several centimetres long, and widen throughout their length from a breadth of 

 •4 mm. to a maximum width of 1 mm., which is attained at their distal extremities. 



The sicula is conspicuous, measuring 2 mm. in length. 



The thecee number seven to eight in 10 mm., and in their general characters 

 resemble those of the typical species. 



15 



